using System.Linq;
using static System.Math;
using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, long.Parse);
        line = Console.ReadLine().Trim().Split(' ');
        var b = Array.ConvertAll(line, long.Parse);
        if (n == 2) getAns2(n, a, b);
        else getAns3(n, a, b);
    }
    static void getAns2(int n, long[] a, long[] b)
    {
        if (a[0] + a[1] != b[0] + b[1]) { Console.WriteLine(-1); return; }
        Console.WriteLine(Abs(a[0] - b[0]));
    }
    static void getAns3(int n, long[] a, long[] b)
    {
        var d = a.Sum() - b.Sum();
        if (d % (n - 2L) != 0) { Console.WriteLine(-1); return; }
        var t = d / (n - 2L);
        for (int i = 0; i < n; i++)
        {
            var w = b[i] - a[i] + t;
            if (w < 0) { Console.WriteLine(-1); return; }
            if (w > 0)
            {
                if (w % 2L != 0) { Console.WriteLine(-1); return; }
            }
        }
        Console.WriteLine(t);
    }
}