#include <bits/stdc++.h>

using namespace std;

int main(void)
{
	cin.tie(0);
	ios::sync_with_stdio(false);

	int n, t;
	vector <int> v;

	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> t;
		v.push_back(t);
	}
	int res = n;

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

	cout << res << '\n';
	return 0;
}