import std.algorithm, std.container, std.conv, std.math, std.range, std.typecons, std.stdio, std.string;
import std.numeric;

auto rdsp(){return readln.splitter;}
void pick(R,T)(ref R r,ref T t){t=r.front.to!T;r.popFront;}
void readV(T...)(ref T t){auto r=rdsp;foreach(ref v;t)pick(r,v);}
void readA(T)(size_t n,ref T[]t){t=new T[](n);auto r=rdsp;foreach(ref v;t)pick(r,v);}

void main()
{
  int n, sx; readV(n, sx);
  int[] x; readA(n, x);

  auto y = x.map!(xi => (xi-sx).abs);

  auto g = y[0];
  foreach (i; 1..n) g = gcd(g, y[i]);

  writeln(g);
}
