#include<iostream>
using namespace std;

int main()
{
	int n, a[100000], i;

	cin >> n;

	for (i = 1; i <= n; i++) cin >> a[i];

	int x = n;
	for (i = n; i > 0; i--) if (a[i] == x) x--;

	cout << x << endl;
}