int getMinimumCost(int k, vector<int> c) {
   
    sort(c.begin(),c.end(),greater<int>());
    int i=0, j=0, ans=0;
    while(i<c.size())
    {
    while(k-- && i<c.size())
    {
       ans += (j+1)*c[i];
       i++;
    }
    j++;
    }
    return ans;
}