#include<iostream>
using namespace std;

int main(){
    int N;
    cin >> N;
    int bar = N;
    int* blocks = new int[N];

    for(int i=0;i<N;i++){
        cin >> blocks[i];
    }

    for(int i=N-1;i>=0;i--){
        if(bar==blocks[i]){
            bar-=1;
        }
    }
    cout << bar << endl;
    return 0;
}