#include<bits/stdc++.h>
using namespace std;
int main() {
	int n;
	cin >> n;
	int s[10001];
	for (int i = 1;i <= n; i++) {
		cin >> s[i];
	}
	int x;
	cin >> x;
	bool f = true;
	for (int i = 1;i <= n; i++) {
		if (s[i] == x) {
			cout << i;
			f = false;
			break;
		}
	}
	if (f) {
		cout << -1;
	}
	return 0;
}