此贴结，以下AC代码

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    priority_queue<int, vector<long long>, greater<int>> pq;
    for (int i = 0; i < n; i++) {
        long long num;
        cin >> num;
        pq.push(num);
    }
    long long cost = 0;
    while (pq.size()>1) {
        long long first = pq.top();
        pq.pop();
        long long second = pq.top();
        pq.pop();
        long long sum = first + second;
        cost+=sum;
        pq.push(sum);
    }
    cout << cost << endl;
    return 0;
}