program main
    implicit none
    integer a, b, c, d
    integer life_t, life_a
    integer i
    read(*,*) a, b, c, d


    life_t = a
    life_a = c

    do i = 1, 1000
        if (mod(i,2) == 0) then
            life_t = life_t - d
        else 
            life_a = life_a - b
        end if

        if (life_a <= 0) then
            write(*,*) "Yes"
            exit
        end if
        if (life_t <= 0) then
            write(*,*) "No"
            exit
        end if
    end do

end program