#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

int v[5000002];
int a[5000002];

int main()
{
    int n,k;
    fin>>n>>k;
    int q = 1;
    for(int i = 1; i<=n;i++){
        fin >> v[i];
        }
    int cnt=n/k;
    int s=0;
    int c=1;
    while(cnt){
        int i = 1;
        sort(v[i],v[i+k]);
        a[c]=v[i];
        c++;
        i=i+k+1;
        cnt--;
    }
    for(int i = 1; i <= c; i++)
        s=s+a[i];
    fout<<s;
    return 0;
}