//#include "stdafx.h"
#include<stdio.h>
#define NMAX 5000010
#define inf 10000100
int q[NMAX],x[NMAX],s,a,i,n,k,in,sf,m,min;
long long rez;
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	scanf("%d%d",&n,&k);
	in=1;
	sf=0;
	min=inf;
	for (i=1;i<=n;++i)
	{
		scanf("%d",&a);
		while (sf>=in&&a<q[sf])
			sf--;
		q[++sf]=a;
		x[sf]=i;
		
		if (i>=k)
			rez+=q[in];
		
		if (i-x[in]+1==k)
			in++;
	}
	printf("%d\n",rez);



	return 0;
}