poj 3053 Fence Repair

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

struct cmp
{
    bool operator() (long long a, long long b)
    {
        return a > b;
    }
};

int main()
{
    priority_queue<long long, vector<long long>, cmp> Q;
    long long n, ans = 0;

    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        long long num;

        cin >> num;
        Q.push(num);
    }

    long long a, b;
    while (Q.size() != 1)
    {
        a = Q.top(); Q.pop();
        b = Q.top(); Q.pop();
        ans += a + b;
        Q.push(a + b);
    }

    cout << ans << endl;

    return 0;
}