#include <iostream>
#include <stdio.h>
#include <fstream>
#define DMAX 5000001
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");
long long sum;
int n, k , lft ,rght , deq[DMAX] , a[DMAX];

int main()
{
    f>>n>>k;
    int i;
    lft=1 ; rght=0;
    for(i=1 ; i<=n ; i++)
        f>>a[i];
    for(i=1 ; i<=n ; i++)
    {
        while(lft <= rght && a[i] <= a[deq[rght]]) rght--;

        deq[++rght]=i;

        if(deq[lft]<=i-k) lft++;
        if(i >= k) sum+=a[deq[lft]];
    }
    g<<sum;
    return 0;
}