b.cpp

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

void solve()
{
    int n;
    scanf("%d", &n);

    int inp[n];
    for(int i = 0; i < n; i++) {
        scanf("%d", &inp[i]);
    }

    sort(inp, inp + n);

    // implement
    // -------++++++++
    ll product = inp[0] * inp[1];
    ll ans = LLONG_MIN;
    for(int i = 2; i < n; i++) {
        ans = max(ans, product * inp[i]);
    }

    product = inp[n - 1] * inp[n - 2];
    for(int i = 0; i < n - 2; i++) {
        ans = max(ans, product * inp[i]);
    }

    printf("%lld\n", ans);
}

int main()
{
    int ncase;
    scanf("%d", &ncase);

    while(ncase--)
        solve();

    return 0;
}