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

using static System.Console;
using static PB10004.Algorithm.Util;

namespace PB10004.Algorithm
{
    class Template
    {
        static void Main(string[] args)
        {
            new C().Solve();
        }
    }
    class A{
        public void Solve(){
            var array = ReadIntArray();
            if((array[0]* array[1]) % 2 == 1){
                WriteLine("Yes");
            }
            else{
                WriteLine("No");
            }
        }
    }
    class B{
        HashSet<string> hash = new HashSet<string>();
        public void Solve(){
            var N = ReadInt();
            var current = "";
            for(int i=0;i<N;i++){
              var tmp = ReadLine();
              if(!hash.Add(tmp)){
                  WriteLine("No");
                  return;
              }
              if(i != 0){
                  if(tmp[0] != current[current.Length-1]){
                      WriteLine("No");
                      return;
                  }
              }
              current = tmp;
            }
            WriteLine("Yes");
        }
    }
    class C{
        public void Solve(){
            var array1 = ReadLongArray();
            var N = array1[0];
            var X = array1[1];
            var array2 = ReadLongArray();
            var array = array2.Select(x=>Math.Abs(x-X)).ToArray();
            var res = array.Aggregate((g,next) => Gcd(g, next));
            WriteLine(res);
        }
    }
    class D{
        public void Solve(){
        }
    }
    public static class Util
    {
        /// <summary>
        /// 標準入力をint型にパースする
        /// </summary>
        /// <returns></returns>
        public static int ReadInt(){
            return int.Parse(ReadLine());
        }
        /// <summary>
        /// 標準入力をint型の配列にする
        /// </summary>
        /// <returns></returns>
        public static int[] ReadIntArray(){
            return ReadLine().Split(' ').Select(x=>int.Parse(x)).ToArray();
        }
        /// <summary>
        /// 標準入力をlong型にパースする
        /// </summary>
        /// <returns></returns>
        public static long ReadLong()
        {
            return long.Parse(ReadLine());
        }
        /// <summary>
        /// 標準入力をlong型の配列にする
        /// </summary>
        /// <returns></returns>
        public static long[] ReadLongArray()
        {
            return ReadLine().Split(' ').Select(long.Parse).ToArray();
        }
        /// <summary>
        /// 一定値の数列を生成する
        /// </summary>
        /// <param name="value"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public static IEnumerable<long> ConstSeq(long value, long length)
        {
            for (int i = 0; i < length; i++)
            {
                yield return value;
            }
        }
        /// <summary>
        /// int配列の累積和を求める
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>
        public static IEnumerable<int> CumulativeSum(IEnumerable<int> array)
        {
            int tmp = 0;
            foreach (var num in array)
                yield return tmp += num;
        }
        /// <summary>
        /// long配列の累積和を求める
        /// </summary>
        /// <param name="array"></param>
        /// <returns></returns>
        public static IEnumerable<long> CumulativeSum(IEnumerable<long> array)
        {
            long tmp = 0;
            foreach (var num in array)
                yield return tmp += num;
        }
        /// <summary>
        /// 最大公約数をユークリッドの互除法で求める
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        public static long Gcd(long a, long b)
        {
            return b == 0 ? a : Gcd(b, a % b);
        }
        /// <summary>
        /// 最小公倍数を求める
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        public static long Lcm(long a, long b)
        {
            return a * b / Gcd(a, b);
        }
    }
}

Measured memory_bytes: 25568