with Ada.Text_IO;
with Ada.Integer_Text_IO;
with Ada.Float_Text_IO;
use Ada.Text_IO;
use Ada.Integer_Text_IO;
use Ada.Float_Text_IO;

procedure hoge is
 a: integer;
 b: integer;
 c: integer;
 d: integer;
 cnt: integer :=0;
begin
 get(a);
 get(b);
 get(c);
 get(d);
 while a>0 and c>0 loop
  if (cnt rem 2)=0 then
   c:=c-b;
  else
   a:=a-d;
  end if;
  cnt:=cnt+1;
 end loop;
 if a<=0 then
  put_line("No");
 else
  put_line("Yes");
 end if;
end hoge;