program main
    use,intrinsic :: iso_fortran_env
    implicit none
    integer(int32):: a,b,c,d,turn

    read*, a,b,c,d
    turn=1
    do while(a > 0 .and. c>0)
        if (turn==1) then
            c=c-b
        else
            a=a-d
        end if
        turn=turn*(-1)
    end do

    if (a>0) then
        print'(a)', 'Yes'
    else
        print'(a)', 'No'
    end if
end program 