//qoj6528
#include <bits/stdc++.h>
using namespace std;

const int N = 5e5 + 10;
int n, a[N];
basic_string<int> pos[N];

struct node{
    int sum, lel, ler, ril, rir;
} t[N*4];

void upd(node &x, node &y, node &z){
    x.sum = y.sum + z.sum;
    x.lel = min(y.lel, y.sum + z.lel);
    x.ler = max(y.ler, y.sum + z.ler);
    x.ril = min(z.ril, z.sum + y.ril);
    x.rir = max(z.rir, z.sum + y.rir);
}
void add(int p, int l, int r, int x, int v){
    if(x < 1 || x > n){
        return;
    }
    if(l == r){
        t[p].sum = v;
        t[p].lel = t[p].ril = min(0, v);
        t[p].ler = t[p].rir = max(0, v);
    } else {
        int mid = l + r >> 1;
        if(x <= mid){
            add(p<<1, l, mid, x, v);
        } else {
            add(p<<1|1, mid+1, r, x, v);
        }
        upd(t[p], t[p<<1], t[p<<1|1]);
    }
}
node ask(int p, int l, int r, int ql, int qr){
    if(qr < l || r < ql){
        return {0, 0, 0, 0, 0};
    } else if(ql <= l && r <= qr){
        return t[p];
    } else {
        int mid = l + r >> 1;
        node x;
        node y = ask(p<<1, l, mid, ql, qr);
        node z = ask(p<<1|1, mid+1, r, ql, qr);
        upd(x, y, z);
        return x;
    }
}
int asksm(int p, int l, int r, int ql, int qr){
    if(qr < l || r < ql){
        return 0;
    } else if(ql <= l && r <= qr){
        return t[p].sum;
    } else {
        int mid = l + r >> 1;
        return asksm(p<<1, l, mid, ql, qr) + 
               asksm(p<<1|1, mid+1, r, ql, qr);
    }
}

bool chk(int val, int x){
    int len = pos[val].size() - 2;
    for(int l = 1; l + x - 1 <= len; ++ l){
        int r = l + x - 1;
        node le = ask(1, 1, n, pos[val][l-1]+1, pos[val][l]-1);
        node ri = ask(1, 1, n, pos[val][r]+1, pos[val][r+1]-1);
        int now = asksm(1, 1, n, pos[val][l], pos[val][r]);
        int lel = le.ril, ler = le.rir;
        int ril = ri.lel, rir = ri.ler;
        int mn = lel + ril + now;
        int mx = ler + rir + now;
        if(mn <= 0 && 0 <= mx){
            return 1;
        }
        if(abs(mx) <= x || abs(mn) <= x){
            return 1;
        }
    }
    return 0;
}

int sequence(int nN, std:: vector<int> A){
    n = nN;
    int nw = 1;
    for(int i = 1; i <= n; ++ i){
        pos[i].push_back(0);
    }
    for(int i = 1; i <= n; ++ i){
        a[i] = A[i-1];
        pos[a[i]].push_back(i);
        add(1, 1, n, i, 1);
    }
    for(int i = 1; i <= n; ++ i){
        pos[i].push_back(n + 1);
    }
    for(int i = 1; i <= n; ++ i){
        for(int j : pos[i]){
            add(1, 1, n, j, 0);
        }
        if(pos[i].size() - 2 > nw){
            int l = nw, r = pos[i].size() - 2;
            while(l < r){
                int mid = l + r + 1 >> 1;
                if(chk(i, mid)){
                    l = mid;
                } else {
                    r = mid - 1;
                }
            }
            nw = max(nw, l);
        }
        for(int j : pos[i]){
            add(1, 1, n, j, -1);
        }
    }
    return nw;
}

#ifndef ONLINE_JUDGE
int main(){
    int n;
    vector<int> v;
    scanf("%d", &n);
    for(int i = 1; i <= n; ++ i){
        int p;
        scanf("%d", &p);
        v.push_back(p);
    }
    printf("%d\n", sequence(n, v));
    return 0;
}
#endif