#include<bits/stdc++.h>
using namespace std;
long long a[1000005],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){
			cout<<i;
			return 0;
		}
	}
	cout<<-1;
	return 0;
}
/**************************************************************
	Problem: 1236
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:366 ms
	Memory:9884 kb
****************************************************************/