program bm
implicit none
integer::A,B,C,D
read*,A,B,C,D
do
    C=C-B
    if(C<=0)then
        print"(A)","Yes"
        stop
    endif
    A=A-D
    if(A<=0)then
        print"(A)","No"
        stop
    endif
end do

contains
end program bm