#include<stdio.h>
int main ()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,i,k,m,nr=0,x;
    long long unsigned sum=0;
    scanf("%d%d",&n,&m);
    int a[m],min=10000000;
    for(i=0;i<m;i++)
   { scanf("%d",&a[i]);
   if(a[i]<min)
{   min=a[i];
nr=1;
}
   else
   if(min==a[i])
      nr++;
      } 
   for(i=m;i<=n;i++)
   {   sum+=min;
   //printf("%d\n",min);
                    
                    scanf("%d",&x);
                    if(a[i%m]==min)
                    nr--;
                 a[i%m]=x;
                    if(x<min)
                  {  min=x;
                  nr=1;
                  }else
                    if(nr==0)
                    {min=a[1];
                    for(k=1;k<=m;k++)
                    if(a[k]<min)
                   { min=a[k];
                   nr=1;
                   }
                   else
                   if(min==a[k])
                   nr++;
                   }
                
                   }
                            printf("%d",sum);
                            return 0;
                            }