program atcoder
   implicit none
   integer A, B, C, D, E, F
   read *, A, B, C, D
   
   A=int(A/D+0.99999999)
   C=int(C/B+0.99999999)
    if (A > C) then
     print *,'No'
    else
     print *,'Yes'
    end if
end program atcoder