結果
| 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 (gcc 12.3.0 + boost 1.83.0) |
| 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 |
（要ログイン）
テストケース
テストケース表示| 入力 | 結果 | 実行時間 実行使用メモリ |
|---|---|---|
| testcase_00 | AC | 2 ms
5,248 KB |
| testcase_01 | AC | 2 ms
5,248 KB |
| testcase_02 | AC | 2 ms
5,248 KB |
| testcase_03 | AC | 2 ms
5,248 KB |
| testcase_04 | AC | 2 ms
5,248 KB |
| testcase_05 | AC | 2 ms
5,248 KB |
| testcase_06 | AC | 226 ms
113,256 KB |
| testcase_07 | AC | 180 ms
92,948 KB |
| testcase_08 | AC | 271 ms
102,316 KB |
| testcase_09 | AC | 260 ms
95,108 KB |
| testcase_10 | AC | 249 ms
94,996 KB |
| testcase_11 | AC | 261 ms
95,124 KB |
| testcase_12 | AC | 256 ms
94,988 KB |
| testcase_13 | AC | 198 ms
94,508 KB |
| testcase_14 | AC | 205 ms
113,128 KB |
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;
}