program deque;
  var a,order:array[1..5000000] of longint;
      k,n,i,left,right,x:longint;
      ans:int64;
      buf:array[1..100000]of byte;
begin
  assign(input,'deque.in');
  reset(input);
  settextbuf(input,buf);
  assign(output,'deque.out');
  rewrite(output);
  readln(n,k);
  left:=1;right:=0;
  for i:=1 to k do
    begin
      readln(x);
      while (right>0)and(a[right]>x)do dec(right);
      inc(right);
      a[right]:=x;
      order[right]:=i;
    end;
  for i:=k+1 to n do
    begin
      ans:=ans+a[left];
      if i=order[left]+k then inc(left);
      readln(x);
      while (right>=left)and(a[right]>x)do dec(right);
      inc(right);
      a[right]:=x;order[right]:=i;
    end;
  ans:=ans+a[left];
  writeln(ans);
  close(input);close(output);
end.