import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.InputMismatchException;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class Main {

	public static void main(String[] args) throws IOException {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		TaskX solver = new TaskX();
		solver.solve(1, in, out);
		out.close();
	}

	static int INF = 1 << 30;
	static long LINF = 1L << 55;
	static int MOD = 1000000007;
	static int[] mh4 = { 0, -1, 1, 0 };
	static int[] mw4 = { -1, 0, 0, 1 };
	static int[] mh8 = { -1, -1, -1, 0, 0, 1, 1, 1 };
	static int[] mw8 = { -1, 0, 1, -1, 1, -1, 0, 1 };

	static class TaskX {

		public void solve(int testNumber, InputReader in, PrintWriter out) {

			int n = in.nextInt();
			long X = in.nextLong();
			long[] x = in.nextLongArray(n);
			Set<Long> set = new TreeSet<>();

			long ans = 0;
			for (int i = 0; i < n; i++) {
				long sa = Math.abs(X - x[i]);
				set.add(sa);
				ans = max(ans, sa);
			}

			for (long l : set) {
				ans = min(ans, gcd(ans, l));
			}

			out.println(ans);

		}

		public static long gcd(long a, long b) {
			return (b == 0) ? a : gcd(b, a % b);
		}
	}

	static class InputReader {
		BufferedReader in;
		StringTokenizer tok;

		public String nextString() {
			while (!tok.hasMoreTokens()) {
				try {
					tok = new StringTokenizer(in.readLine(), " ");
				} catch (IOException e) {
					throw new InputMismatchException();
				}
			}
			return tok.nextToken();
		}

		public int nextInt() {
			return Integer.parseInt(nextString());
		}

		public long nextLong() {
			return Long.parseLong(nextString());
		}

		public double nextDouble() {
			return Double.parseDouble(nextString());
		}

		public int[] nextIntArray(int n) {
			int[] res = new int[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextInt();
			}
			return res;
		}

		public int[] nextIntArrayDec(int n) {
			int[] res = new int[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextInt() - 1;
			}
			return res;
		}

		public int[] nextIntArray1Index(int n) {
			int[] res = new int[n + 1];
			for (int i = 0; i < n; i++) {
				res[i + 1] = nextInt();
			}
			return res;
		}

		public long[] nextLongArray(int n) {
			long[] res = new long[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextLong();
			}
			return res;
		}

		public long[] nextLongArrayDec(int n) {
			long[] res = new long[n];
			for (int i = 0; i < n; i++) {
				res[i] = nextLong() - 1;
			}
			return res;
		}

		public long[] nextLongArray1Index(int n) {
			long[] res = new long[n + 1];
			for (int i = 0; i < n; i++) {
				res[i + 1] = nextLong();
			}
			return res;
		}

		public InputReader(InputStream inputStream) {
			in = new BufferedReader(new InputStreamReader(inputStream));
			tok = new StringTokenizer("");
		}
	}

	static long max(long... n) {
		long ret = n[0];
		for (int i = 0; i < n.length; i++) {
			ret = Math.max(ret, n[i]);
		}
		return ret;
	}

	static int max(int... n) {
		int ret = n[0];
		for (int i = 0; i < n.length; i++) {
			ret = Math.max(ret, n[i]);
		}
		return ret;
	}

	static long min(long... n) {
		long ret = n[0];
		for (int i = 0; i < n.length; i++) {
			ret = Math.min(ret, n[i]);
		}
		return ret;
	}

	static int min(int... n) {
		int ret = n[0];
		for (int i = 0; i < n.length; i++) {
			ret = Math.min(ret, n[i]);
		}
		return ret;
	}

	static String zeroPad(String str, int len) {
		return String.format("%" + len + "s", str).replace(" ", "0");
	}

}


Measured memory_bytes: 45308