#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=0;b<m;b++){
        if(a[b]==n){
            cout<<b+1;
            k=1;
            break;
        }
    }
    if(k!=1){
        cout<<"-1"; 
    }
    return 0;
}
 
/**************************************************************
	Problem: 1154
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:17 ms
	Memory:2072 kb
****************************************************************/