#961916 (C++17(gcc12)) No.778 クリスマスツリー

• 問題: No.778 クリスマスツリー
• ユーザー: T101010101
• 提出日時: 2024-03-19 23:05:19
• 言語: C++17(gcc12) (gcc 12.3.0 + boost 1.87.0)
• 結果: AC
• 実行時間: 271 ms / 2,000 ms
• コード長: 21,215 bytes
• コンパイル時間: 5,224 ms
• コンパイル使用メモリ: 320,336 KB
• 実行使用メモリ: 113,256 KB
• 最終ジャッジ日時: 2024-09-30 05:52:37
• 合計ジャッジ時間: 8,663 ms
• ジャッジサーバーID （参考情報）: judge1 / judge2

ファイルパターン	結果
sample	AC * 3
other	AC * 12

ソースコード

#pragma region Macros

#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,fma,abm,mmx,avx,avx2")

#include <bits/extc++.h>
// #include <atcoder/all>
// using namespace atcoder;
using namespace std;
using namespace __gnu_pbds;

// #include <boost/multiprecision/cpp_dec_float.hpp>
// #include <boost/multiprecision/cpp_int.hpp>
// namespace mp = boost::multiprecision;
// using Bint = mp::cpp_int;
// using Bdouble = mp::number<mp::cpp_dec_float<256>>;

#define pb emplace_back
#define int ll
#define endl '\n'

#define sqrt __builtin_sqrt
#define cbrt __builtin_cbrt
#define hypot __builtin_hypot

using ll = long long;
using ld = long double;
const ld PI = acosl(-1);
const int INF = 1 << 30;
const ll INFL = 1LL << 61;
const int MOD = 998244353;
// const int MOD = 1000000007;

const ld EPS = 1e-10;
const bool equals(ld a, ld b) { return fabs((a) - (b)) < EPS; }

const vector<int> dx = {0, 1, 0, -1, 1, 1, -1, -1}; // → ↓ ← ↑ ↘ ↙ ↖ ↗
const vector<int> dy = {1, 0, -1, 0, 1, -1, -1, 1};

struct Edge {
    int from, to;
    ll cost;
    Edge(int to, ll cost) : to(to), cost(cost) {}
    Edge(int from, int to, ll cost) : from(from), to(to), cost(cost) {}
};

chrono::system_clock::time_point  start, now;
__attribute__((constructor))
void constructor() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(10);
    start = chrono::system_clock::now();
}

__int128_t POW(__int128_t x, int n) {
    __int128_t ret = 1;
    assert(n >= 0);
    if (x == 1 or n == 0) ret = 1;
    else if (x == -1 && n % 2 == 0) ret = 1; 
    else if (x == -1) ret = -1; 
    else if (n % 2 == 0) {
        assert(x < INFL);
        ret = POW(x * x, n / 2);
    } else {
        assert(x < INFL);
        ret = x * POW(x, n - 1);
    }
    return ret;
}
int per(int x, int y) { // x = qy + r (0 <= r < y) を満たすq
    assert(y != 0);
    if (x >= 0 && y > 0) return x / y;
    if (x >= 0 && y < 0) return x / y - (x % y < 0);
    if (x < 0 && y < 0) return x / y + (x % y < 0);
    return x / y - (x % y < 0); //  (x < 0 && y > 0) 
}
// int perl(ld x, ld y) { // perld(4.5, 2.1) = 2  // TODO
//     if (-EPS < x && x < 0 or 0 < x && x < EPS) x = 0;
//     if (-EPS < y && y < 0 or 0 < x && x < EPS) y = 0;
//     assert(!equals(y, 0));
//     if (x >= 0 && y > 0) return floor(x / y)+EPS;
//     if (x >= 0 && y < 0) return floor(x / y) - (x - floor(x/y)*y < -EPS);
//     if (x < 0 && y < 0) return floor(x / y) + (x - floor(x/y)*y < -EPS);
//     return floor(x / y) - (x - floor(x/y)*y < -EPS); //  (x < 0 && y > 0) 
// }
int mod(int x, int y) { // x = qy + r (0 <= r < y) を満たすr
    assert(y != 0);
    if (x >= 0) return x % y;
    __int128_t ret = x % y; // (x < 0)
    ret += (__int128_t)abs(y) * INFL;
    ret %= abs(y);
    return ret;
}
// ld modl(ld x, ld y) { // TODO
//     assert(!equals(y, 0));
//     if (x >= -EPS) return (x - floor(x/y)*y);
//     ld ret = x - floor(x/y)*y; // (x < 0)
//     ret += abs(y) * INFL; // TODO : オーバーフローする?
//     ret = x - floor(x/abs(y))*abs(y);
//     return ret;
// }
// int floor(int x, int y) { // TODO
//     assert(y != 0);
//     if (b < 0) a = -a, b = -b;
//     return a >= 0 ? a / b : (a + 1) / b - 1;
// }
// int ceil(int x, int y) { // TODO
// assert(y != 0);
//     if (b < 0) a = -a, b = -b;
//     return a > 0 ? (a - 1) / b + 1 : a / b;
// }
// int floorl(ld x, ld y) { return 0; } // TODO
// int ceill(ld x, ld y) { return 0; } // TODO
// int gauss(int x, int y) {
//     assert(y != 0);
//     return x / y;
// } // 整数部分(未verify)
// int gauss(ld x, ld y) { return 0; } // TODO

pair<int, int> max(const pair<int, int> &a, const pair<int, int> &b) {
    if (a.first > b.first or a.first == b.first && a.second > b.second) {
        return a;
    }
    return b;
}
pair<int, int> min(const pair<int, int> &a, const pair<int, int> &b) {
    if (a.first < b.first or a.first == b.first && a.second < b.second) {
        return a;
    }
    return b;
}

template <class T> bool chmax(T &a, const T& b) {
    if (a < b) { a = b; return true; }
    return false;
}
template <class T> bool chmin(T &a, const T& b) {
    if (a > b) { a = b; return true; }
    return false;
}
template <class T> T mid(T a, T b, T c) {
    return a + b + c - max({a, b, c}) - min({a, b, c});
}
template <class T> void sort(T &a, T &b, T &c, bool rev = false) {
    if (rev == false) { 
        if (a > b) swap(a, b);
        if (a > c) swap(a, c);
        if (b > c) swap(b, c);
    } else {
        if (c > b) swap(c, b);
        if (c > a) swap(c, a);
        if (b > a) swap(b, a);
    }
}
template <class T> void sort(T &a, T &b, T &c, T &d, bool rev = false) {
    if (rev == false) { 
        if (a > b) swap(a, b); if (a > c) swap(a, c);  if (a > d) swap(a, d);
        if (b > c) swap(b, c); if (b > d) swap(b, d);
        if (c > d) swap(c, d);
    } else {
        if (d > c) swap(d, c); if (d > b) swap(d, b); if (d > a) swap(d, a);
        if (c > b) swap(c, b); if (c > a) swap(c, a);
        if (b > a) swap(b, a);
    }
}

int countl_zero(int x) { return __builtin_clzll(x); }
int countl_one(int x) {
    int ret = 0; while (x % 2) { x /= 2; ret++; }
    return ret;
}
int countr_zero(int x) { return __builtin_ctzll(x); }
int countr_one(int x) {
    int ret = 0, k = 63 - __builtin_clzll(x);
    while (k != -1 && (x & (1LL << k))) { k--; ret++; }
    return ret;
}
int popcount(int x) { return __builtin_popcountll(x); }
int unpopcount(int x) { return 64 - __builtin_clzll(x) - __builtin_popcountll(x); }

int top_bit(int x) { return 63 - __builtin_clzll(x);} // 2^kの位
int bot_bit(int x) { return __builtin_ctz(x);} // 2^kの位
int MSB(int x) { return 1 << (63 - __builtin_clzll(x)); } // mask
int LSB(int x) { return (x & -x); } // mask

int bit_width(int x) { return 64 - __builtin_clzll(x); } // 桁数
int ceil_log2(int x) { return 63 - __builtin_clzll(x); }
int bit_floor(int x) { return 1 << (63 - __builtin_clzll(x)); }
int floor_log2(int x) { return 64 - __builtin_clzll(x-1); }
int bit_ceil(int x) { return 1 << (64 - __builtin_clzll(x-1)) - (x==1); }

int hamming(int a, int b) { return popcount(a ^ b); }
int compcnt(int x) { return (popcount(x^(x >> 1)) + (x&1)) / 2; }

class UnionFind {
public:
	UnionFind() = default;
    UnionFind(int N) : par(N), sz(N, 1) {
        iota(par.begin(), par.end(), 0);
    }

	int root(int x) {
		if (par[x] == x) return x;
		return (par[x] = root(par[x]));
	}

	bool unite(int x, int y) {
		int rx = root(x);
		int ry = root(y);

        if (rx == ry) return false;
		if (sz[rx] < sz[ry]) swap(rx, ry);

		sz[rx] += sz[ry];
		par[ry] = rx;

        return true;
	}

	bool issame(int x, int y) { return (root(x) == root(y)); }
	int size(int x) { return sz[root(x)]; }

    vector<vector<int>> groups(int N) {
        vector<vector<int>> G(N);
        for (int x = 0; x < N; x++) {
            G[root(x)].push_back(x);
        }
		G.erase(
            remove_if(G.begin(), G.end(),
                [&](const vector<int>& V) { return V.empty(); }),
                    G.end());
        return G;
    }
private:
	vector<int> par;
	vector<int> sz;
};

template<int mod> class Modint{
public:
    int val = 0;
    Modint(int x = 0) { while (x < 0) x += mod; val = x % mod; }
    Modint(const Modint &r) { val = r.val; }

    Modint operator -() { return Modint(-val); } // 単項
    Modint operator +(const Modint &r) { return Modint(*this) += r; }
    Modint operator +(const int &q) { Modint r(q); return Modint(*this) += r; }
    Modint operator -(const Modint &r) { return Modint(*this) -= r; }
    Modint operator -(const int &q) { Modint r(q); return Modint(*this) -= r; }
    Modint operator *(const Modint &r) { return Modint(*this) *= r; }
    Modint operator *(const int &q) { Modint r(q); return Modint(*this) *= r; }
    Modint operator /(const Modint &r) { return Modint(*this) /= r; }
    Modint operator /(const int &q) { Modint r(q); return Modint(*this) /= r; }
    
    Modint& operator ++() { val++; if (val >= mod) val -= mod; return *this; } // 前置
    Modint operator ++(signed) { ++*this; return *this; } // 後置
    Modint& operator --() { val--; if (val < 0) val += mod; return *this; }
    Modint operator --(signed) { --*this; return *this; }
    Modint &operator +=(const Modint &r) { val += r.val; if (val >= mod) val -= mod; return *this; }
    Modint &operator +=(const int &q) { Modint r(q); val += r.val; if (val >= mod) val -= mod; return *this; }
    Modint &operator -=(const Modint &r) { if (val < r.val) val += mod; val -= r.val; return *this; }
    Modint &operator -=(const int &q) { Modint r(q);  if (val < r.val) val += mod; val -= r.val; return *this; }
    Modint &operator *=(const Modint &r) { val = val * r.val % mod; return *this; }
    Modint &operator *=(const int &q) { Modint r(q); val = val * r.val % mod; return *this; }
    Modint &operator /=(const Modint &r) {
        int a = r.val, b = mod, u = 1, v = 0;
        while (b) {int t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v);}
        val = val * u % mod; if (val < 0) val += mod;
        return *this;
    }
    Modint &operator /=(const int &q) {
        Modint r(q); int a = r.val, b = mod, u = 1, v = 0;
        while (b) {int t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v);}
        val = val * u % mod; if (val < 0) val += mod;
        return *this;
    }

    bool operator ==(const Modint& r) { return this -> val == r.val; }
    bool operator <(const Modint& r) { return this -> val < r.val; }
    bool operator >(const Modint& r) { return this -> val > r.val; }
    bool operator !=(const Modint& r) { return this -> val != r.val; }
};

using mint = Modint<MOD>;
// using Mint = modint998244353;

istream &operator >>(istream &is, mint& x) {
    int t; is >> t;
    x = t;
    return (is);
}
ostream &operator <<(ostream &os, const mint& x) {
    return os << x.val;
}
mint modpow(const mint &x, int n) {
    assert(n >= 0); // TODO: n <= -1
    if (n == 0) return 1;
    mint t = modpow(x, n / 2);
    t = t * t;
    if (n & 1) t = t * x;
    return t;
}

int modpow(__int128_t x, int n, int mod) {
    assert(n >= 0 && mod > 0); // TODO: n <= -1
    __int128_t ret = 1;
    while (n > 0) {
        if (n % 2 == 1) ret = ret * x % mod;
        x = x * x % mod;
        n /= 2;
    }
    return ret;
}

int modinv(__int128_t x, int mod) {
    assert(mod > 0 && x > 0);
    if (x == 1) return 1;
    return mod - modinv(mod % x, mod) * (mod / x) % mod;
}

istream &operator >>(istream &is, __int128_t& x) {
    string S; is >> S;
    __int128_t ret = 0;
    int f = 1;
    if (S[0] == '-') f = -1; 
    for (int i = 0; i < S.length(); i++)
        if ('0' <= S[i] && S[i] <= '9')
            ret = ret * 10 + S[i] - '0';
    x = ret * f;
    return (is);
}
ostream &operator <<(ostream &os, __int128_t x) {
    ostream::sentry s(os);
    if (s) {
        __uint128_t tmp = x < 0 ? -x : x;
        char buffer[128];
        char *d = end(buffer);

        do {
            --d;
            *d = "0123456789"[tmp % 10];
            tmp /= 10;
        } while (tmp != 0);

        if (x < 0) {
            --d;
            *d = '-';
        }
        int len = end(buffer) - d;

        if (os.rdbuf()->sputn(d, len) != len) {
            os.setstate(ios_base::badbit);
        }
    }
    return os;
}

__int128_t stoll(string &S) {
    __int128_t ret = 0;
    int f = 1;
    if (S[0] == '-') f = -1; 
    for (int i = 0; i < S.length(); i++)
        if ('0' <= S[i] && S[i] <= '9')
            ret = ret * 10 + S[i] - '0';
    return ret * f;
}
__int128_t gcd(__int128_t a, __int128_t b) {
    return b ? gcd(b, a % b) : a;
}
__int128_t lcm(__int128_t a, __int128_t b) {
    return a / gcd(a, b) * b;
    // lcmが__int128_tに収まる必要あり
}

string to_string(ld x, int k) { // xの小数第k位までをstring化する
    assert(k >= 0);
    stringstream ss;
    ss << setprecision(k + 2) << x;
    string s = ss.str();
    if (s.find('.') == string::npos) s += '.';
    int pos = s.find('.');
    for (int i = 0; k >= (int)s.size() - 1 - pos; i++) s += '0';
    s.pop_back();
    if (s.back() == '.') s.pop_back();
    return s;

    // stringstream ss; // 第k+1位を四捨五入して第k位まで返す
    // ss << setprecision(k + 1) << x;
    // string s = ss.str();
    // if (s.find('.') == string::npos) s += '.';
    // int pos = s.find('.');
    // for (int i = 0; k > (int)s.size() - 1 - pos; i++) s += '0';
    // if (s.back() == '.') s.pop_back();
    // return s;
}

string to_string(__int128_t x) {
    string ret = "";
    if (x < 0) {
        ret += "-";
        x *= -1;
    }
    while (x) {
        ret += (char)('0' + x % 10);
        x /= 10;
    }
    reverse(ret.begin(), ret.end());
    return ret;
}
string to_string(char c) {
    string s = "";
    s += c;
    return s;
}

struct SXor128 {
    uint64_t x = 88172645463325252LL;
    unsigned Int() {
        x = x ^ (x << 7);
        return x = x ^ (x >> 9);
    }
    unsigned Int(unsigned mod) {
        x = x ^ (x << 7);
        x = x ^ (x >> 9);
        return x % mod;
    }
    unsigned Int(unsigned l, unsigned r) {
        x = x ^ (x << 7);
        x = x ^ (x >> 9);
        return x % (r - l + 1) + l;
    }
    double Double() {
        return double(Int()) / UINT_MAX;
    }
} rnd;

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

template<class T> size_t HashCombine(const size_t seed,const T &v) {
    return seed^(hash<T>()(v)+0x9e3779b9+(seed<<6)+(seed>>2));
}
template<class T,class S> struct hash<pair<T,S>>{
    size_t operator()(const pair<T,S> &keyval) const noexcept {
        return HashCombine(hash<T>()(keyval.first), keyval.second);
    }
};
template<class T> struct hash<vector<T>>{
    size_t operator()(const vector<T> &keyval) const noexcept {
        size_t s=0;
        for (auto&& v: keyval) s=HashCombine(s,v);
        return s;
    }
};
template<int N> struct HashTupleCore{
    template<class Tuple> size_t operator()(const Tuple &keyval) const noexcept{
        size_t s=HashTupleCore<N-1>()(keyval);
        return HashCombine(s,get<N-1>(keyval));
    }
};
template <> struct HashTupleCore<0>{
    template<class Tuple> size_t operator()(const Tuple &keyval) const noexcept{ return 0; }
};
template<class... Args> struct hash<tuple<Args...>>{
    size_t operator()(const tuple<Args...> &keyval) const noexcept {
        return HashTupleCore<tuple_size<tuple<Args...>>::value>()(keyval);
    }
};

vector<mint> _fac, _finv, _inv;
void COMinit(int N) {
    _fac.resize(N + 1);
    _finv.resize(N + 1);
    _inv.resize(N + 1);
    _fac[0] = _fac[1] = 1;
    _finv[0] = _finv[1] = 1;
    _inv[1] = 1;
    for (int i = 2; i <= N; i++) {
        _fac[i] = _fac[i-1] * mint(i);
        _inv[i] = -_inv[MOD % i] * mint(MOD / i);
        _finv[i] = _finv[i - 1] * _inv[i];
    }
}

mint FAC(int N) {
    if (N < 0) return 0;
    return _fac[N];
}
mint COM(int N, int K) {
    if (N < K) return 0;
    if (N < 0 or K < 0) return 0;
    return _fac[N] * _finv[K] * _finv[N - K];
}
mint PERM(int N, int K) {
    if (N < K) return 0;
    if (N < 0 or K < 0) return 0;
    return _fac[N] *  _finv[N - K];
}
mint NHK(int N, int K) {
    if (N == 0 && K == 0)  return 1;
    return COM(N + K - 1, K);
}

#pragma endregion

struct Bit_Vector {
    int n, m;
    vector<uint64_t> bit;
    vector<int> sum;

    Bit_Vector(int n) : n(n), m((n + 63) / 64), bit(m), sum(m + 1) {}
    void set(int k) { bit[k / 64] |= 1ULL << (k % 64); }
    void build() {
        for (int i = 0; i < m; i++) {
            sum[i + 1] = sum[i] + __builtin_popcountll(bit[i]);
        }
    }
    bool operator[](int k) const { return (bit[k / 64] >> (k % 64)) & 1ULL; }
   
    int rank(int r, bool b) const {
        int one = sum[r / 64];
        if (r & 63) one += __builtin_popcountll(bit[r / 64] & ((1ULL << (r % 64)) - 1));
        return b ? one : r - one;
    }
    
    int rank(int l, int r, bool b) const { return rank(r, b) - rank(l, b); }
};

template<typename T>
struct WaveletMatrix {
    int maxlog, n;
    vector<Bit_Vector> matrix;
    vector<int> zero_cnt;
    vector<vector<ll>> cs;

    WaveletMatrix(vector<T> data, ll max_v) : n(data.size()) {
        T min_v = n ? *min_element(data.begin(), data.end()) : 0;
        assert(0 <= min_v);
        maxlog = max(64 - __builtin_clzll(max_v), 1);
        matrix.resize(maxlog, Bit_Vector(n));
        cs.resize(maxlog, vector<ll>(n + 1));
        zero_cnt.resize(maxlog);
        vector<T> zero(n), one(n);

        for (int i = 0; i < maxlog; i++) {
            int z = 0, o = 0;
            for (int j = 0; j < n; j++) {
                if ((data[j] >> (maxlog - 1 - i)) & 1) {
                    one[o++] = data[j];
                    matrix[i].set(j);
                } 
                else {
                    zero[z++] = data[j];
                    zero_cnt[i]++;
                }
            }
            matrix[i].build();
            data.swap(zero);
            for (int i = 0; i < o; i++) data[z + i] = one[i];
            for (int j = 0; j < n; j++) cs[i][j + 1] = cs[i][j] + data[j];
        }
    }

    T access(int k) {
        T ret = 0;
        for (int i = 0; i < maxlog; i++) {
            bool bit = matrix[i][k];
            ret = (ret << 1) | bit;
            k = matrix[i].rank(k, bit) + zero_cnt[i] * bit;
        }
        return ret;
    }

    int rank(int l, int r, T x) {
        for (int i = 0; i < maxlog; i++) {
            bool bit = (x >> (maxlog - 1 - i)) & 1;
            l = matrix[i].rank(l, bit) + zero_cnt[i] * bit;
            r = matrix[i].rank(r, bit) + zero_cnt[i] * bit;
        }
        return r - l;
    }
   
    T kth_smallest(int l, int r, int k) const {
        assert(0 <= k && k < r - l);
        T res = 0;
        for (int i = 0; i < maxlog; i++) {
            int zero = matrix[i].rank(l, r, 0);
            bool bit = k >= zero;
            l = matrix[i].rank(l, bit) + zero_cnt[i] * bit;
            r = matrix[i].rank(r, bit) + zero_cnt[i] * bit;
            res |= (T(1) << (maxlog - 1 - i)) * bit;
            k -= zero * bit;
        }
        return res;
    }

    T kth_largest(int l, int r, int k) { return kth_smallest(l, r, r - l - k - 1); }

    tuple<int, int, int> rank_all(int l, int r, T x) const {
        int lt_cnt = 0, eq_cnt = r - l , mt_cnt = 0;
        for (int i = 0; i < maxlog; i++) {
            int tmp = r - l;
            bool bit = (x >> (maxlog - 1 - i)) & 1;
            l = matrix[i].rank(l, bit) + zero_cnt[i] * bit;
            r = matrix[i].rank(r, bit) + zero_cnt[i] * bit;
            int d = tmp - (r - l);
            eq_cnt -= d;
            (bit ? lt_cnt : mt_cnt) += d;
        }
        return { lt_cnt, eq_cnt, mt_cnt };
    }

    int range_freq(int l, int r, T lower, T upper) {
        auto l_cnt = get<0>(rank_all(l, r, lower));
        auto r_cnt = get<0>(rank_all(l, r, upper));
        return r_cnt - l_cnt;        
    }

    T prev_value(int l, int r, T upper) {
        int cnt = get<0>(rank_all(l, r, upper));
        return cnt == 0 ? T(-1) : kth_smallest(l, r, --cnt);
    } 

    T next_value(int l, int r, T lower) {
        int cnt = get<0>(rank_all(l, r, lower));
        return cnt == r - l ? T(-1) : kth_smallest(l, r, cnt);
    }

    ll sum_less_than(int l, int r, T x) {
        ll ret = 0;
        for (int i = 0; i < maxlog; i++) {
            bool bit = (x >> (maxlog - 1 - i) & 1);
            if (bit) ret += cs[i][matrix[i].rank(r, 0)] - cs[i][matrix[i].rank(l, 0)];
            l = matrix[i].rank(l, bit) + zero_cnt[i] * bit;
            r = matrix[i].rank(r, bit) + zero_cnt[i] * bit;
        }
        return ret;
    }

    ll range_sum(int l, int r, T lower, T upper) { 
        return sum_less_than(l, r, upper) - sum_less_than(l, r, lower);
    }
};

vector<int> flag; // dfs用
vector<int> in; // 頂点iに行きがけで訪れた時刻
vector<int> out; // 頂点iに帰りがけで訪れた時刻
vector<int> id; // 時刻iに訪れた頂点の番号
vector<int> depth; // 根からの深さ
int cnt = 0;
void dfs(const vector<vector<int>> &G, int v) {
    in[v] = cnt++;
    id.pb(v);

    flag[v] = true; 
    for (auto nv : G[v]) { 
        if (flag[nv]) continue;
        depth[nv] = depth[v] + 1;
        dfs(G, nv);
    }

    out[v] = cnt++;
    id.pb(v);
}

signed main() {
    int N;
    cin >> N;

    vector<vector<int>> G(N);
    for (int i = 1; i < N; i++) {
        int p;
        cin >> p;
        G[p].pb(i);
    }

    flag.assign(N, false);
    depth.resize(N);
    in.resize(N);
    out.resize(N);

    dfs(G, 0);

    WaveletMatrix<int> WM(id, 1e6 + 1);

    int ans = 0;
    for (int i = 0; i < N; i++) {
        int l = in[i];
        int r = out[i];
        ans += WM.range_freq(l, r + 1, i + 1, 1e6) / 2;
    }
    cout << ans << endl;
}