func main()
	var n: int :: cui@inputInt()
	var m: int :: cui@inputInt()
	var a: []int :: #[n]int
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
	end for
	var b: []int :: #[m]int
	for i(0, m - 1)
		do b[i] :: cui@inputInt()
	end for
	
	var ans: int :: -1
	for i(0, n * m - 1)
		if(a[i % n] = b[i % m])
			do ans :: i + 1
			break i
		end if
	end for
	
	do cui@print("\{ans}\n")
end func