#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define mem(a, b) memset(a, b, sizeof(a))
#define rep(i, a, b) for (int i = a; i <= b; ++i)
#define rrep(i, a, b) for (int i = a; i >= b; --i)
#define FOR(i, a, b) for (int i = a; i < b; ++i)
#define pb push_back
#define MP make_pair
#define all(v) v.begin(), v.end()
#define clr(v) v.clear()
#define isEven(x) !(x & 1)
#define yes cout<<"YES"<<endl
#define no cout<<"NO"<<endl
int main() {
	ios::sync_with_stdio ( false );
	cin.tie ( 0 );
	int n, k;
	vector<int>a ( n );
	cin >> n;
	rep ( i, 0, n - 1 ) cin >> a[i];
	cin >> k;
	rep ( i, 0, n - 1 ) {
		if ( a[i] == k ) {
			cout << i;
			return 0;
		}
	}
	cout<<"-1";
	return 0;
}