#include<stdio.h>
using namespace std;
FILE *f,*g;
int k,n,i,s,p,u,a[50000001],d[50000001];
int main()
{
f=fopen("deque.in","r");
g=fopen("deque.out","w");
fscanf(f,"%d",&n);
fscanf(f,"%d",&k);
for(i=1;i<=n;i++)
	fscanf(f,"%d",&a[i]);
for(i=1;i<=n;i++)
{
	while(p<=u&&a[d[u]]>=a[i]) u--;
	u++;
	d[u]=i;
	if(i-d[p]==k) p++;
	if(i>=k) s=s+a[d[p]];
}
fprintf(g,"%d",s);
fclose(f);
fclose(g);
return 0;
}