program Project1;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var a,b:text;n,i,m,s,k:real;
begin
  { TODO -oUser -cConsole Main : Insert code here }
  assign(a,'problem.in');
  assign(b,'problem.out');
  reset(a);
  read(a,n);
  read(a,m);
  s:=0;
  For i:=1 to n do
  s:=s+i;
  if s mod m =0 then k:= s div m else k:=0;
  rewrite(b);
  write(b,s);
  close(a);
  close(b);
end.