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

typedef long long ll;
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define each(itr,c) for(__typeof(c.begin()) itr=c.begin(); itr!=c.end(); ++itr)
#define all(x) (x).begin(),(x).end()
#define mp make_pair
#define pb push_back
#define fi first
#define se second

int main()
{
    int n;
    cin >>n;
    vector<int> a(n);
    rep(i,n) scanf(" %d", &a[i]);

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

    cout << now << endl;
    return 0;
}