#include<bits/stdc++.h>
using namespace std;
long long n,a[1000005],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: zhengzihao
	Language: C++
	Result: Accepted
	Time:315 ms
	Memory:9884 kb
****************************************************************/