#include <iostream>
using namespace std;

int main() {
    int n;
    while (cin >> n) { 
        int a[n];
        for(int i=0;i<n;i++)
        {
            cin>>a[i];
        }

        int x;cin>>x;
        int i;
        for( i=0;i<n;i++)
        {
            if(x==a[i]){cout<<i<<endl;break;}
        }    
        if(i==n&&(x!=a[n-1]))cout<<"-1"<<endl;
    }
}