#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,m,cnt;
    int a[101];
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>a[i];
    }
    cin>>m;
    for(int i=0;i<n;i++){
        if(a[i]==m){
            cout<<i+1;
            cnt+=1;
            break;
        }
    }
    if(cnt==0)
    cout<<"-1";
    return 0;
}
/**************************************************************
	Problem: 1154
	User: luyanchen
	Language: C++
	Result: Wrong Answer
****************************************************************/