#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <list>
#include <deque>
#include <algorithm>

using namespace std;

int main() {
	int n;
	vector<int>a;
	cin >> n;

	a.push_back(0);
	for (int i = 0; i < n; i++) {
		int value;
		cin >> value;
		a.push_back(value);
	}

	int ans = n;
	for (int i = n; i != 0; i--) {
		if (a[i] == ans) {
			ans--;
		}
	}
	cout << ans << endl;
	return 0;
}