答案

#include <iostream>
using namespace std;
int a[40];
int main(){
int n,k,b=-1;
cin>>n;
for (int i=0;i<n;i++)cin>>a[i];
cin>>k;
for (int i=0;i<n;i++){
if (a[i]==k){
b=i+1;
break;
}
}
cout<<b;
return 0;
}