#include <stdio.h>
#include <stdlib.h>
#define NMAX 5000001

int main()
{
    int deque[NMAX],v[NMAX];
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k,i,x,st=1,dr=0;
    long long sum=0;
    scanf("%d %d",&n,&k);
    for (i=1;i<=n;i++)
    {
        scanf("%d",&x);
        while (st<=dr && i-v[st]>=k) st=(st+1)%NMAX;
        while (st<=dr && x-deque[dr-1]<0) dr=(NMAX+dr-1)%NMAX;
        deque[dr]=x;
        v[dr]=i;
        dr=(dr+1)%NMAX;
        if (i>=k) sum+=deque[st];
    }
    printf("%lld",sum);
    fclose(stdout);
    fclose(stdin);
    return 0;
}