program main
      implicit none
      integer(4) :: n, m, i
      integer(4) :: a, b, c, d 

      read *, a, b, c, d

      i = 1
      do
        if ( mod(i,2) == 0 ) then
          a = a - d
          if ( a <= 0 ) then
            print *, 'No'
            exit
          end if
        else
          c = c - b
          if ( c <= 0 ) then
            print *, 'Yes'
            exit
          end if
        end if
        i = i + 1
      end do

end program main
