#include <stdio.h>
FILE *f=fopen("deque.in","r");
FILE *g=fopen("deque.out","w");
int n,k,v[500001],deq[500001];

int main(void){
	register int i,j;
	
	fscanf(f,"%d %d",&n,&k);
	deq[1]=1;
	fscanf(f,"%d",&v[1]);
	int sum=0;
	int p=1,u=1;
	for(i=2;i<=n;i++){
		fscanf(f,"%d",&v[i]);
		while(p<=u && v[deq[u]]>=v[i])
			u--;
		deq[++u]=i;
		if(i-deq[p]==k)
			p++;
		if(i>=k)
			sum+=v[deq[p]];
	}
	fprintf(g,"%d",sum);
	return 0;
}