#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
// --------------------------------------------------------
#define FOR(i,l,r) for (ll i = (l); i < (r); ++i)
#define RFOR(i,l,r) for (ll i = (r)-1; (l) <= i; --i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define SORT(c) sort(ALL(c))
#define RSORT(c) sort(RALL(c))
#define MIN(c) *min_element(ALL(c))
#define MAX(c) *max_element(ALL(c))
#define COUNT(c,v) count(ALL(c),(v))
#define SZ(c) ((ll)(c).size())
#define BIT(b,i) (((b)>>(i)) & 1)
#define PCNT(b) __builtin_popcountll(b)
#define P0(i) (((i) & 1) == 0)
#define P1(i) (((i) & 1) == 1)
#define LB(c,v) distance((c).begin(), lower_bound(ALL(c), (v)))
#define UB(c,v) distance((c).begin(), upper_bound(ALL(c), (v)))
#define UQ(c) SORT(c), (c).erase(unique(ALL(c)), (c).end())
#define elif else if
#ifdef _LOCAL
    #define debug_bar cerr << "--------------------\n";
    #define debug(x) cerr << "l." << __LINE__ << " : " << #x << " = " << (x) << '\n'
    #define debug_pair(x) cerr << "l." << __LINE__ << " : " << #x << " = (" << x.first << "," << x.second << ")\n";
    template<class T> void debug_line(const vector<T>& ans, int l, int r, int L = 0) { cerr << "l." << L << " :"; for (int i = l; i < r; i++) { cerr << ' ' << ans[i]; } cerr << '\n'; }
#else
    #define cerr if (false) cerr
    #define debug_bar
    #define debug(x)
    #define debug_pair(x)
    template<class T> void debug_line([[maybe_unused]] const vector<T>& ans, [[maybe_unused]] int l, [[maybe_unused]] int r, [[maybe_unused]] int L = 0) {}
#endif
template<class... T> void input(T&... a) { (cin >> ... >> a); }
void print() { cout << '\n'; }
template<class T> void print(const T& a) { cout << a << '\n'; }
template<class T, class... Ts> void print(const T& a, const Ts&... b) { cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; }
template<class T> void cout_line(const vector<T>& ans, int l, int r) { for (int i = l; i < r; i++) { if (i != l) { cout << ' '; } cout << ans[i]; } cout << '\n'; }
template<class T> bool chmin(T& a, const T b) { if (b < a) { a = b; return 1; } return 0; }
template<class T> bool chmax(T& a, const T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> T SUM(const vector<T>& A) { return accumulate(ALL(A), T(0)); }
template<class T> vector<T> cumsum(const vector<T>& A, bool offset = true) { int N = A.size(); vector<T> S(N+1, 0); for (int i = 0; i < N; i++) { S[i+1] = S[i] + A[i]; } if (not offset) { S.erase(S.begin()); } return S; }
ll mod(ll x, ll m) { assert(m != 0); return (x % m + m) % m; }
ll ceil(ll a, ll b) { if (b < 0) { return ceil(-a, -b); } assert(b > 0); return (a < 0 ? a / b : (a + b - 1) / b); }
ll floor(ll a, ll b) { if (b < 0) { return floor(-a, -b); } assert(b > 0); return (a > 0 ? a / b : (a - b + 1) / b); }
ll powint(ll x, ll n) { assert(n >= 0); if (n == 0) { return 1; }; ll res = powint(x, n>>1); res *= res; if (n & 1) { res *= x; } return res; }
pair<ll,ll> divmod(ll a, ll b) { assert(b != 0); ll q = floor(a, b); return make_pair(q, a - q * b); }
ll bitlen(ll b) { if (b <= 0) { return 0; } return (64LL - __builtin_clzll(b)); }
ll digit_len(ll n) { assert(n >= 0); if (n == 0) { return 1; } ll sum = 0; while (n > 0) { sum++; n /= 10; } return sum; }
ll digit_sum(ll n) { assert(n >= 0); ll sum = 0; while (n > 0) { sum += n % 10; n /= 10; } return sum; }
ll digit_prod(ll n) { assert(n >= 0); if (n == 0) { return 0; } ll prod = 1; while (n > 0) { prod *= n % 10; n /= 10; } return prod; }
ll xor_sum(ll x) { assert(0 <= x); switch (x % 4) { case 0: return x; case 1: return 1; case 2: return x ^ 1; case 3: return 0; } assert(false); }
string toupper(const string& S) { string T(S); for (int i = 0; i < (int)T.size(); i++) { T[i] = toupper(T[i]); } return T; }
string tolower(const string& S) { string T(S); for (int i = 0; i < (int)T.size(); i++) { T[i] = tolower(T[i]); } return T; }
int a2i(const char& c) { assert(islower(c)); return (c - 'a'); }
int A2i(const char& c) { assert(isupper(c)); return (c - 'A'); }
int d2i(const char& d) { assert(isdigit(d)); return (d - '0'); }
char i2a(const int& i) { assert(0 <= i && i < 26); return ('a' + i); }
char i2A(const int& i) { assert(0 <= i && i < 26); return ('A' + i); }
char i2d(const int& i) { assert(0 <= i && i <= 9); return ('0' + i); }
using P = pair<ll,ll>;
using VP = vector<P>;
using VVP = vector<VP>;
using VS = vector<string>;
using VVS = vector<VS>;
using VI = vector<int>;
using VVI = vector<VI>;
using VVVI = vector<VVI>;
using VLL = vector<ll>;
using VVLL = vector<VLL>;
using VVVLL = vector<VVLL>;
using VB = vector<bool>;
using VVB = vector<VB>;
using VVVB = vector<VVB>;
using VD = vector<double>;
using VVD = vector<VD>;
using VVVD = vector<VVD>;
using VLD = vector<ld>;
using VVLD = vector<VLD>;
using VVVLD = vector<VVLD>;
const ld EPS = 1e-10;
const ld PI  = acosl(-1.0);
constexpr ll MOD = 1000000007;
// constexpr ll MOD = 998244353;
constexpr int inf = (1 << 30) - 1;   // 1073741824 - 1
constexpr ll INF = (1LL << 62) - 1;  // 4611686018427387904 - 1
// --------------------------------------------------------
#include <atcoder/segtree>
using namespace atcoder;

// 1点更新・区間最小
using S = int;
S op1(S a, S b) { return min(a, b); }
S e1() { return +inf; }
S op2(S a, S b) { return max(a, b); }
S e2() { return -inf; }


template<class T = ll>
vector<T> compress(vector<T>& X) {
    int N = X.size();
    vector<T> XS(X);  // 圧縮前の座標配列 (圧縮後の座標と1対1対応)

    // 重複削除
    sort(XS.begin(), XS.end());
    XS.erase(unique(XS.begin(), XS.end()), XS.end());

    // 圧縮後の座標の割り当て
    for (int i = 0; i < N; i++) {
        X[i] = lower_bound(XS.begin(), XS.end(), X[i]) - XS.begin();
    }
    return XS;
}


int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);

    int N; input(N);
    VI A(N); REP(i,N) input(A[i]);

    auto ZA = compress(A);
    int M = SZ(ZA);
    VVI E(M);
    REP(i,N) E[M-1-A[i]].push_back(i);

    VVI dp_L(N+1, VI(N, +inf));
    VVI dp_R(N+1, VI(N, -inf));

    vector<segtree<S, op2, e2>> seg_L(N+1, segtree<S, op2, e2>(N));  // range max
    vector<segtree<S, op1, e1>> seg_R(N+1, segtree<S, op1, e1>(N));  // range min

    ll ans = 1;
    REP(k,M) {  // 高い方から k+1 本目を追加
        RFOR(j,1,k+1) {
            for (auto i : E[k]) {
                int r = seg_R[j].prod(i+1, N);
                int l = seg_L[j].prod(0, i);
                if (r != +inf) {
                    chmax(ans, j+1);
                    chmin(dp_L[j+1][i], r);
                    seg_L[j+1].set(r, op2(seg_L[j+1].get(r), i));
                }
                if (l != -inf) {
                    chmax(ans, j+1);
                    chmax(dp_R[j+1][i], l);
                    seg_R[j+1].set(l, op1(seg_R[j+1].get(l), i));
                }
            }
        }
        for (auto i : E[k]) {
            // 1 本目
            dp_L[1][i] = i;
            dp_R[1][i] = i;
            seg_L[1].set(i, i);
            seg_R[1].set(i, i);
        }
    }
    print(ans);

    return 0;
}