#include<iostream.h>
#include<fstream.h>
#include<stdio.h>
#define N 5000001
typedef struct deque
{long elem[N],nel,prim,ultim;};
long a,n,k,i,j,b[N];
long long s=0;
deque q;

void addEnd(deque &q,long x)
{q.nel++;
q.elem[q.ultim++]=x;}

long delBeg(deque &q)
{q.nel--;
return q.elem[q.prim++];}

long delEnd(deque &q)
{q.nel--;
return q.elem[--q.ultim];}

int main()
{q.nel=q.prim=q.ultim=0;
ifstream f1("deque.in");
ofstream f2("deque.out");
f1>>n>>k;
b[0]=0;
for(i=1;i<=n;i++)
      {f1>>a;
      while(q.nel!=0&&a<q.elem[q.ultim-1])
             delEnd(q);
      addEnd(q,a);
      b[q.prim]++;
      b[q.prim+1]=q.nel-1;
      b[q.ultim-1]=1;
      if(((q.nel==1&&q.prim==i-k)||(q.prim<i-k&&q.nel<k)||(i==k&&b[q.prim]>1))&&b[q.prim]<k)
             s+=q.elem[q.prim];
      else
             if(q.nel==k||b[q.prim]==k||q.prim==i-k||(i==k&&b[q.prim]==1))
                   s+=delBeg(q);}
f2<<s;
f1.close();
f2.close();
return 0;}