program main
  implicit none
  integer*8::x,y,x2,y2
  read *,x,y,x2,y2
  if(x2.lt.x.and.y2.lt.y) then
     if(x2*y.eq.x*y2) then
        print '(i0)', MAX(x,y)+1
        return
     end if
  endif
  print '(i0)', MAX(x,y)
end program main