#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
  ll n, sum = 0, ssum = 0;
  cin >> n;
  for (ll i = 0; i < n; i++){
    ll x;
    cin >> x;
    sum += x;
    ssum += x*x;
  }
  cout << n*ssum - sum*sum;
  return 0;
}