#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    int b[5000010],a[5000010],n,ma;
    long long suma=0;

    fin>>n>>ma;
    for (int i=1; i<=n; i++)
    {
        fin>>a[i];
    }
    int k=0,ls=0;
    int j=0;
    for (int i=1; i<=n; i++)
    {

        while (k>0 && a[i]<a[b[k]] && k>=j)
            k--;
        k++;
        b[k]=i;
        while (b[j]<i-ma+1 && j<=k)
            j++;
        if (i-ma+1>=1)
        {
            suma+=a[b[j]];
        }
    }
    fout<<suma;
    return 0;
}