Particle Accelerator II

#include <iostream>
#include <cmath>
#include <vector>
#include <cassert>
#include <algorithm>
#include <set>
using namespace std;
#define rep(i, a, b) for(int i=a;i<(b);++i)
#define all(x) begin(x),end(x)
#define sz(x) int((x).size())
using ll = long long;
using pii = pair<int,int>;
using vi = vector<int>;


multiset<int> S;

int main() {
  int n;
  cin >> n;
  rep(i,0,n) {
    int x;
    cin >> x;
    S.insert(x);
  }
  ll cost = 0;
  while (S.size() > 1) {
    auto it = S.begin();
    ll a = *it;
    S.erase(it);
    it = S.begin();
    ll b = *it;
    S.erase(it);
    S.insert(a+b);
    cost += a*b;
  }
  cout << cost << '\n';
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED