import qualified Data.Map as M

calc visits [a,b,m,r] iter = case M.lookup r' visits of
    Just x -> iter' - x
    Nothing -> calc visits' [a,b,m,r'] (iter')
    where
        iter' = iter + 1
        r' = (a * r + b) `rem` m
        visits' = M.insert r' iter' visits


main = do
    line <- getLine
    let list = map (\x -> read x :: Int) $ words line
    print $ calc M.empty list 0