#include <bits/stdc++.h>

using namespace std;
const int N = 2000;
/*
4
-1 3 5 3
3
*/
int a[N];
int k, n, x;
int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    cin >> x;
    for (int i = 1; i <= n; i++) {
        if (a[i] == x) {
            k = i;
            printf("%d", k);
            break;
        }
    }
    if (k == 0)
        printf("-1");
    return 0;
}