import Data.List

main = do
    [a,b,c,d] <- map read.words <$> getLine
    putStrLn.show.answer a b c d $ lcm c d

answer a b c d e = (b-a+1) -abc-abd+abe where
    ac_start = if mod a c == 0 then a else a + (c-mod a c)
    bc_end = b - mod b c
    abc = (div bc_end c - div ac_start c + 1)
    ad_start = if mod a d == 0 then a else a + (d-mod a d)
    bd_end = b - mod b d
    abd = (div bd_end d - div ad_start d + 1)
    ae_start = if mod a e == 0 then a else a + (e-mod a e)
    be_end = b - mod b e
    abe = (div be_end e - div ae_start e + 1)