var toInt = x=>parseInt(x,10);
var toIntArr = arr=>arr.map(x=>toInt(x));
var abs = x=>x>0?x:-x;
function min(){var rest = arguments,val=rest[0];for(var i=1;i<rest.length;i++)if(rest[i]<val)val = rest[i];return val}
function max(){var rest = arguments,val=rest[0];for(var i=1;i<rest.length;i++)if(rest[i]>val)val = rest[i];return val}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
 
function Main(input){
	var input = input.split('\n');
	var temp = toIntArr(input[0].split(' '));
	var n = temp[0];
	var x = temp[1];
	var xs = toIntArr(input[1].split(' '));

	var ys = xs.map(e=>abs(e-x));

	function gcd(a,b){
		if(b===0) return a;
		return gcd(b,a%b);
	}

	var ans = ys[0];
	for(var i = 0; i < n-1; i++){
		ans = gcd(ans,ys[i+1]);
	}
	console.log(ans);
}