program main
  
  implicit none
  integer :: a, b, c, d
  
  read(*,*) a, b, c, d

  !while( a <= 0 .or. c <= 0 ) 
  do
    c = c - b
    if( c <= 0 ) exit
    a = a - d
    if( a <= 0 ) exit
  end do
  
  if( a <= 0 )then
    print*, "No"
  else
    print*, "Yes"
  end if
end program main
