GPT答：

7i24.cn

```cpp
#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int N, M;
    cin >> N >> M;

    vector<int> candies(N);
    for (int i = 0; i < N; i++) {
        cin >> candies[i];
    }

    sort(candies.begin(), candies.end(), greater<int>());

    int sum = 0;
    int max_candy = -1;
    
    for (int i = 0; i < N; i++) {
        if (i % M == 0) {
            if (max_candy != -1) {
                sum += max_candy;
            }
            max_candy = -1;
        }
        
        if (candies[i] > max_candy) {
            max_candy = candies[i];
        }
        
        if ((i + 1) % M == 0 && max_candy != -1) {
            sum += max_candy;
            max_candy = -1;
        }
        
        if ((i + 1) == N && max_candy != -1) {
            sum += max_candy;
        }
   }

   cout << sum << endl;

   return 0;
}
```