#include<stdio.h>
using namespace std;
FILE *f,*g;
int k,n,i,p,u,a[5000002],d[5000002];
long long s;
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]);
p = 1;
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,"%lld",s);
fclose(f);
fclose(g);
return 0;
}