program deque1;
var f,g:text;
    n,i,k,p,c:longint;
    a,coada:array[1..5000000] of longint;
    s:int64;

begin
 assign (f,'deque.in'); reset (f);
 assign (g,'deque.out'); rewrite (g);
 readln(f,n,k);
 for i:=1 to n do
  readln (f,a[i]);
  p:=1; c:=0;   s:=0;
  for i:=1 to n do
  begin
  while (p<=c) and (a[i]<=a[coada[c]]) do
   c:=c-1;
  c:=c+1;
  coada[c]:=i;
  if i>=k then
  begin
   if coada[p]=i-k then
    p:=p+1;
   s:=s+a[coada[p]];
  end;
 end;
  write (g,s);
  close (F); close (G);
end.