#include <stdio.h>
#define NMAX 5000005
#define ll long long
int n,k,A[NMAX],deq[NMAX],inc,sf;
ll rez;
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	int i;
	scanf("%d%d",&n,&k);
	for (i=1; i<=n; i++)
	{
		scanf("%d",&A[i]);
		while (sf!=inc && A[deq[sf-1]]>=A[i]) sf--;
		deq[sf++]=i;
		if (i-deq[inc]>=k) inc++;
		if (i>=k)
			rez+=A[deq[inc]];
	}
	printf("%lld\n",rez);
	return 0;
}