#include <iostream>
#include <vector>
using namespace std;
int main(void) {
	int n;
	cin >> n;
	vector<int> v(n);
	for (int i = 0; i < n; ++i) cin >> v[i];
	int x = n;
	for (int i = n - 1; i >= 0; --i) {
		if (v[i] == x) --x;
	}
	cout << x << endl;
	return 0;
}