1543B - Customising the Track - CodeForces Solution

#include <bits/stdc++.h>
#include <ext/numeric>
#include <ext/pb_ds/assoc_container.hpp>
#define fast cin.tie(0); cin.sync_with_stdio(0);
#define ll long long
#define ull unsigned long long
#define ld long double
#define oo (ll)1e9
#define OO (ll)1e18
#define PI acos(-1)
#define LL __int128
using namespace std;
using namespace __gnu_pbds;
template<class T> using ordered_set = tree<T, null_type , less<T> , rb_tree_tag , tree_order_statistics_node_update> ;
template<class T> using ordered_multiset = tree<T, null_type, less_equal<T>,rb_tree_tag, tree_order_statistics_node_update>;
const ll mod = 1e9 + 7;
const int MOD = 998244353;
const ld eps = 1e-6;
int tt = 1;
int test;
const int N = 2e5 + 5;
ll a[N];
int n;
void solve()
{
    cin >> n;
    ll sum = 0;
    for(int i = 0 ; i < n ; i++) cin >> a[i] , sum += a[i];
    ll rem = sum % n;
    cout << rem * (n - rem) << '\n';

}
int main()
{
    fast
    cin >> tt;
    while(tt--)
        solve();
    return 0;
}