#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
struct io {
  io() {
    ios::sync_with_stdio(false);
    cin.tie(0);
  }
};
const int INF = INT_MAX;
const long long int LLINF = 1LL << 60;
const long long int MOD = 1000000007;
const double EPS = 1e-9;
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
int main(void) {
  int N, X;
  cin >> N >> X;
  vector<int> x(N);
  for (int i = 0; i < (N); ++i) cin >> x[i];
  for (int i = 0; i < (N); ++i) x[i] = abs(X - x[i]);
  if (N == 1) {
    cout << (x[0]) << '\n';
    return 0;
  }
  int g = gcd(x[0], x[1]);
  for (size_t i = 2; i < N; i++) {
    g = gcd(g, x[i]);
  }
  cout << (g) << '\n';
  return 0;
}
