"use strict";

function _slicedToArray(arr, i) { return _arrayWithHoles(arr) || _iterableToArrayLimit(arr, i) || _nonIterableRest(); }

function _nonIterableRest() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

function _iterableToArrayLimit(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

function _arrayWithHoles(arr) { if (Array.isArray(arr)) return arr; }

function main(input) {
  var lines = input.split('\n');

  var _splitNum = splitNum(lines[0]),
      _splitNum2 = _slicedToArray(_splitNum, 2),
      N = _splitNum2[0],
      X = _splitNum2[1];

  var xs = splitNum(lines[1]).slice(0, N);
  var rels = xs.map(function (x) {
    return Math.abs(x - X);
  });
  var D = rels.length > 1 ? rels.reduce(gcd) : rels[0];
  console.log(D);
}

function gcd(a, b) {
  while (b > 0) {
    if (a < b) {
      var _ref = [b, a];
      a = _ref[0];
      b = _ref[1];
      continue;
    }

    var _ref2 = [b, a % b];
    a = _ref2[0];
    b = _ref2[1];
  }

  return a;
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));

function splitNum(line) {
  return line.split(/\s+/).map(function (n) {
    return parseInt(n);
  });
}
