program ABC164_B
  integer::A,B,C,D
  read(*,*)A,B,C,D
  do i=1,100
     C=C-B
     if(C<=0) then
        k=1
        exit
     end if
     A=A-D
     if(A<=0) then
        k=0
        exit
     end if
  end do
  if(k==1) then
     write(*,*)'Yes'
  else
     write(*,*)'No'
  end if
end program ABC164_B