#include<bits/stdc++.h>
using namespace std;
int main()
{
	int m,b,n;
	int k=0;
	cin>>m;
	int a[m];
	for(b=0;b<=m-1;b++){
		cin>>a[b];
	}cin>>n;
	for(b=1;b<=m;b++){
		if(a[b]==n){
			cout<<b+1;
			k=1;
			break;
		}
	}
	if(k!=1){
		cout<<"-1"; 
	}
	return 0;
}

/**************************************************************
	Problem: 1154
	User: houshanglin
	Language: C++
	Result: Wrong Answer
****************************************************************/