只有第二组数据能过，其他都WA，请问怎么回事？
```cpp
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main() {
int num = 0;
cin >> num;
vector<int> piles;

for (int i = 0; i < num; ++i) {
int temp;
cin >> temp;
piles.push_back(temp);
}

if (num == 1) {
cout << piles[0];
return 0;
}

sort(piles.begin(), piles.end());

unsigned long temp = piles[0] + piles[1];
unsigned long result = temp;

for (int j = 2; j < num; ++j) {
temp = temp + piles[j];
result += temp;
}

cout << result;
system("pause");
}
```