codeforces Ilya and Matrix

http://codeforces.com/contest/313/problem/C

 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;
 long long a[]; int main()
 {
     int n;
     scanf("%d",&n);
     for(int i=; i<n; i++)
     {
         scanf("%lld",&a[i]);
     }
     sort(a,a+n);
     long long ans=,ans1=;
     int k=,j=;
     for(int i=n-; i>=; i--)
     {
         ans1+=a[i];
         j++;
         if(j==k)
         {
             ans+=ans1;
             k=k*;
         }
     }
     printf("%lld\n",ans);
     return ;
 }