codeforces Ilya and Matrix

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

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
long long a[3000000];

int main()
{
    int n;
    scanf("%d",&n);
    for(int i=0; i<n; i++)
    {
        scanf("%lld",&a[i]);
    }
    sort(a,a+n);
    long long ans=0,ans1=0;
    int k=1,j=0;
    for(int i=n-1; i>=0; i--)
    {
        ans1+=a[i];
        j++;
        if(j==k)
        {
            ans+=ans1;
            k=k*4;
        }
    }
    printf("%lld
",ans);
    return 0;
}