#include <stdio.h>
int main()
{freopen("deque.in","r",stdin);
freopen("deque.out","w",stdout);
int a[100],n,i,k,min,s=0,j;
scanf("%d%d",&n,&k);
for(i=1;i<=n;++i)
scanf("%d",&a[i]);
for(i=1;i<=n-k+1;++i)
{for(min=a[i],j=i;j<=i+k-1;++j)
if(a[j]<min) min=a[j];
s+=min;}
printf("%d",s);
return 0;
}