noname15 (KPLANK)

#include<bits/stdc++.h>
#define FORn(i, n) for(int i=1; i<=(n); i++)
#define FORRn(i, n) for(int i=(n); i>=1; i--)
using namespace std;

int n, res;
deque<int> s;
int main(){
    cin>>n;
    vector<int> h(n+2, 0), l(n+2, 0), r(n+2, 0);
    s.push_back(0);
    FORn(i, n){
        cin>>h[i];
        while(h[i]<=h[s.back()]) s.pop_back();
        l[i]=s.back();
        s.push_back(i);
    }
    s={n+1};
    FORRn(i, n){
        while(h[i]<=h[s.front()]) s.pop_front();
        r[i]=s.front();
        s.push_front(i);
    }
    FORn(i, n){
        if(h[i]<=res) continue;
        if(r[i]-l[i]-1>=h[i]) res=h[i];
    }
    cout<<res;
}