Problem J

#include<iostream>
#include<cstdio>
using namespace std;

int main(){
    int t; cin >> t;
    for(int i = 1; i <= t; i++){
        int k; cin >> k;
        unsigned long long int a[k];
        for(int j = 0; j < k; j++){
            cin >> a[j];
        }
        unsigned long long int result = 1;
        if(k == 1){
            result = a[0] * a[0];
        }
        else{
            result = a[0] * a[k-1];
        }
        cout << "Case " << i << ": " << result;
        //printf("Case %d: %lld", i, result);
        if(i != t) cout << endl;
    }
}