   program abc164b
      implicit none
      integer::a,b,c,d
      integer::i

         read *, a,b,c,d

         do i=1,100
            c=c-b
            if (c<=0) then
               print *, 'Yes'
               exit
            end if

            a=a-d
            if (a<=0) then
               print *, 'No'
               exit
            end if
         end do

   end program abc164b