#include<bits/stdc++.h>
using namespace std;
int n,a[1000001],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){
			cout<<i;
			return 0;
		}
	}
	cout<<"-1";
	return 0;
}

/**************************************************************
	Problem: 1236
	User: linyifan
	Language: C++
	Result: Accepted
	Time:300 ms
	Memory:5980 kb
****************************************************************/