#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &x: a) cin >> x;

    int ans = n;

    for(int i=n-1;i >= 0;i--){
        if(ans == a[i]){
            ans--;
        }
    }

    cout << ans << endl;
    return 0;
}