ff

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include <algorithm>
#include <map>
#include <set>
#include <string>
#define form(i, n) for (int (i) = 0; (i) < (n); ++ (i))

using namespace std;

int gcd(int a, int b) {
    if (a < b)
        swap(a, b);
    if (a % b == 0)
        return b;
    else
        return gcd(b, a % b);
}

int main(void) {
    //ios_base::sync_with_stdio(false);
    //cin.tie(NULL);

    //freopen("input.txt", "r", stdin);

    int n, X;
    scanf("%d%d", &n, &X);
    int x[n + 1];
    for (int i = 0; i < n; ++ i)
        scanf("%d", x + i);
    x[n ++] = X;
    sort(x, x + n);
    int g = x[1] - x[0];
    for (int i = 2; i < n; ++ i)
        g = gcd(g, x[i] - x[i - 1]);
    printf("%d\n", g);
    return 0;
}