module Main where

import Data.List (findIndex)

type Input  = (Int, Int, [Int], [Int])
type Output = Int

parse :: String -> Input
parse s =
    let
        reads = \pos ->
            map read
            . words
            . pos
            $ lines s

        [n, m] =
            reads head

        a =
            reads (!! 1)

        b =
            reads (!! 2)
    in
        (n, m, a, b)

solve :: Input -> Output
solve (n, m, a, b) =
    maybe (-1) succ
    . findIndex (uncurry (==))
    . take (lcm n m)
    . zip (cycle a)
    $ cycle b

render :: Output -> String
render = show

main :: IO ()
main =
    interact
        ( render
        . solve
        . parse
        )