knigi

#include <iostream>
#include <algorithm>

using namespace std;

int main()
{
    int  n, m, m1c, n1c, lcount=0;
    cin >> n >> m;
    n1c = n-1;
    int nizxi[n];
    for(int i=0; i<n; i++) cin >> nizxi[i];
    sort(nizxi, nizxi+n);
    while(n1c>=0){
    lcount+=(nizxi[n1c]*2);
    n1c-=m;
    }
    cout << lcount;
    return 0;
}