using static System.Math;
using System.Linq;
using System.Collections.Generic;
using System;

public class P
{
    public int aa { get; set; }
    public int bb { get; set; }
}

public class Hello
{
    public static int n, m;
    static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        n = int.Parse(line[0]);
        m = int.Parse(line[1]);
        line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        line = Console.ReadLine().Trim().Split(' ');
        var b = Array.ConvertAll(line, int.Parse);
        var ps = new List<P>();
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                if (a[i] == b[j]) ps.Add(new P { aa = i, bb = j });
        getAns(ps);
    }
    static void getAns(List<P> ps)
    {
        var ans = int.MaxValue;
        if (ps.Count() == 0) { Console.WriteLine(-1); return; }
        var tmax = Max(n, m);
        foreach (var x in ps)
        {
            for (int L = 0; L <= tmax; L++)
                for (int k = 0; k <= tmax; k++)
                {
                    if ((m * L + x.bb - x.aa) % n == 0)
                    {
                        var p = m * L + x.bb;
                        ans = Min(ans, p);
                    }
                }
        }
        Console.WriteLine(ans + 1);
    }
}