#include<iostream>
#include<string>
#include<algorithm>
#include<cctype>
#include<set>
#include<bitset>
#include<math.h>
#include<map>
#include<queue>
#include<iomanip>
using namespace std;
using ll = long long;



int main()
{
    int n, p, now;
    cin >> n;
    vector<int> v(n);
    for (int i = 0; i < n; i++) {
        cin >> v[i];
        if (v[i] == n) p = i;
    }
    now = n -1;
    for (int i = p - 1; i >= 0; i--){
        if (v[i] == now) now--;
    }
    cout << now << endl;
}