get_string(String) :-
  current_input(Input),
  read_string(Input, ' \n', '', _, String).
 
get_number(Number) :-
  get_string(String),
  number_string(Number, String).

main :-
  get_number(A),
  get_number(B),
  get_number(C),
  get_number(D),
  X is (A+D-1)//D,
  Y is (C+B-1)//B,
  (X>=Y -> writeln('Yes');writeln('No')).
