map

#include <bits/stdc++.h>
using namespace std;
map<int, int>mp;

int main()
{
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		int x;
		cin >> x;
		if (mp[x] == 0)
			mp[x] = i;
	}
	int m;
	cin >> m;
	if (mp[m] == 0)
		cout << -1;
	else
		cout << mp[m];
	return 0;
}