program sss;
var f,g:text;
   n,i,u,p,k:longint;
   s:int64;
   a,c:array[1..5000000] of longint;
begin
assign(f,'deque.in'); reset(f);
assign(g,'deque.out'); rewrite(g);
readln(f,n,k);
  for i:=1 to n do
    read(f,a[i]);
    p:=1;
    u:=0;
    s:=0;
  for i:=1 to n do
     begin
       while (u>=p) and (a[i]<a[c[u]]) do
         u:=u-1;
         u:=u+1;
         c[u]:=i;
           if i>=k then
             begin
               if c[p]=i-k then
                 p:=p+1;
                 s:=s+a[c[p]];
             end;
     end;
  write(g,s);
close(f);
close(g);
end.