#include<stdio.h>

int v[5000011],x[5000001],i,j,k,l,m,n,p,q;
long long int sum;

int main(){

freopen("deque.in","r",stdin);
freopen("deque.out","w",stdout);

scanf("%d %d",&n,&k);

p=q=1;
for(i=1;i<=n;i++)
        {scanf("%d",&v[i]);
        while(x[q]<i-k+1&&q<=p)
                q++;
       while(v[i]<v[x[p]]&&p>=q)
                p--;
      p++;
      x[p]=i;
      if(i>=k)
        sum+=v[x[q]];
       }

printf("%lld",sum);
return 0;}