#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;

int a[100010];

int main()
{
	ll N;
	cin >> N;

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

	ll cnt = N;
	for (int i = N-1; i >= 0; i--) {
		if (a[i] == cnt)
			cnt--;
	}

	cout << cnt<< endl;
	return 0;
}