using System;
using System.Linq;
using System.Collections.Generic;

namespace Contest
{
    class Program
    {
        static void Main(string[] args)
        {
            ABC109.C();
        }
        
        class ABC109
        {
            public static void A()
            {
                Console.WriteLine((Read.Int() * Read.Int()) % 2 == 1 ? "Yes" : "No");
            }
            public static void B()
            {
                var N = Read.Int();
                var W = Enumerable.Range(0, N).Select(i => Read.Str()).ToArray();
                if (W.Distinct().Count() < N)
                {
                    Console.WriteLine("No"); return;
                }
                for (int i = 0; i < N - 1; ++i)
                {
                    if (W[i].Last() != W[i + 1][0]) { Console.WriteLine("No"); return; }
                }
                Console.WriteLine("Yes");
            }
            public static void C()
            {
                var N = Read.Int();
                var X = Read.Long();
                var x = Read.LongN();
                var gcd = Math.Abs(x[0] - X);
                for(int i = 1; i < N; ++i)
                {
                    gcd = Util.GCD(gcd, Math.Abs(x[i] - X));
                }
                Console.WriteLine(gcd);
            }
            public static void D()
            {
                var H = Read.Int();
                var W = Read.Int();
                var A = Read.LongMatrix(H, W);
                List<int[]> list = new List<int[]>();
                for(int i = 0; i < H; ++i)
                {
                    for(int j = 0; j < W - 1; ++j)
                    {
                        if (A[i, j] % 2 > 0)
                        {
                            list.Add(new int[] { i, j, i, j + 1 });
                            A[i, j + 1] += 1;
                        }
                    }
                }
                for (int i = 0; i < H - 1; ++i)
                {
                    int j = W - 1;
                    if (A[i, j] % 2 > 0)
                    {
                        list.Add(new int[] { i, j, i + 1, j });
                        A[i + 1, j] += 1;
                    }
                }
                Console.WriteLine(list.Count);
                foreach(var v in list)
                {
                    Console.WriteLine(String.Join(" ", v.Select(i => i + 1)));
                }
            }
        }


        class Util
        {
            public static long GCD(long a, long b)
            {
                while (b > 0)
                {
                    var c = a % b;
                    a = b;
                    b = c;
                }
                return a;
            }
        }

        static class Read
        {
            static Queue<string> queue = new Queue<string>();
            static void Enqueue() { var ss = Console.ReadLine().Split(' '); foreach (var s in ss) { queue.Enqueue(s); } }
            public static int Int() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt32(queue.Dequeue()); }
            public static long Long() { if (queue.Count == 0) { Enqueue(); } return Convert.ToInt64(queue.Dequeue()); }
            public static string Str() { if (queue.Count == 0) { Enqueue(); } return queue.Dequeue(); }
            public static int[] IntN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray(); }
            public static long[] LongN() { return Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray(); }
            public static string[] StrN() { return Console.ReadLine().Split(' '); }
            public static Tuple<int, int>[] TupleInt(int n) { List<Tuple<int, int>> list = new List<Tuple<int, int>>(); for (int i = 0; i < n; ++i) { var ab = Read.IntN(); list.Add(new Tuple<int, int>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<long, long>[] TupleLong(int n) { List<Tuple<long, long>> list = new List<Tuple<long, long>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<long, long>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<string, string>[] TupleStr(int n) { List<Tuple<string, string>> list = new List<Tuple<string, string>>(); for (int i = 0; i < n; ++i) { var ab = Read.StrN(); list.Add(new Tuple<string, string>(ab[0], ab[1])); } return list.ToArray(); }
            public static Tuple<double, double>[] TupleDouble(int n) { List<Tuple<double, double>> list = new List<Tuple<double, double>>(); for (int i = 0; i < n; ++i) { var ab = Read.LongN(); list.Add(new Tuple<double, double>(ab[0], ab[1])); } return list.ToArray(); }
            public static long[,] LongMatrix(int r, int c)
            {
                var mat = new long[r, c];
                for (int i = 0; i < r; ++i)
                {
                    var x = Read.LongN();
                    for (int j = 0; j < c; ++j)
                    {
                        mat[i, j] = x[j];
                    }
                }
                return mat;
            }
            public static Dictionary<int, HashSet<int>> AdjacencyList(int N, int M)
            {
                Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
                for (int i = 0; i <= N; ++i)
                {
                    dict.Add(i, new HashSet<int>());
                }
                for (int i = 0; i < M; ++i)
                {
                    var ab = Read.IntN();
                    dict[ab[0]].Add(ab[1]);
                    dict[ab[1]].Add(ab[0]);
                }
                return dict;
            }
        }
    }
}


Measured memory_bytes: 21088