#include <iostream>
#include <fstream>
using namespace std;
int a[500001],n,k,d[400000],i,f,b,s;
int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");
    fin>>n>>k;
    for(i=1;i<=n;i++)fin>>a[i];
    f=1;
    b=1;
    d[1]=1;
    for(i=2;i<=n;i++)
    {
        if(a[i]<=a[d[b]])a[d[b]]=a[i];
            else {b++;a[d[b]]=a[i];}
        if(d[f]==i-k)f++;
    }
    for(i=1;i<=b;i++)s+=a[d[i]];
    fout<<s;
    //for(i=1;i<=f;i++)cout<<d[i];
    fin.close();
    fout.close();
    return 0;
}