program atcoder
   implicit none
   integer A, B, C, D, X, Y
   read *, A, B, C, D
   
   X=int((A+D-1)/D)
   Y=int((C+B-1)/B)
   if (X >= Y) then
     print *,'Yes'
    else
     print *,'No'
    end if
end program atcoder