#include<bits/stdc++.h>
using namespace std;
int n,a[100001],x;
int main(){
	cin>>n;
	for(int i=1;i<=n;i++) scanf("%d",&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: fzy001
	Language: C++
	Result: Time Limit Exceed
****************************************************************/