#include<stdio.h>
int v[5000001],q[5000001];
int main()
{
	freopen("deque.in","r",stdin);
	freopen("deque.out","w",stdout);
	long long s=0;
	int n,k,i,p,u;
	scanf("%d%d",&n,&k);
	p=1;
	u=0;
	for(i=1;i<=n;i++){
		scanf("%d",&v[i]);
		while(p<=u&&v[q[u]]>=v[i]){
			--u;
		}
		q[++u]=i;
		if(i-q[p]==k){
			p++;
		}
		if(i>=k)
			s+=v[q[p]];
	}
	printf("%lld\n",s);
	return 0;
}