#![allow(unused_imports)]

#[macro_use]
mod _input {
    use std::fmt;
    use std::io::{self, Read};
    use std::str::{self, FromStr};

    macro_rules! input {
        ($($name:ident : $t:tt), *,) => {
            input!($($name: $t),*)
        };
        ($($name:ident : $t:tt), *) => {
            let ($($name, )*) = {
                let mut _scanned = ::_input::Scanned::new(::std::io::stdin(), 1024);
                $(let $name = _read_value!(_scanned, $t);)*
                ($($name, )*)
            };
            $(let _ = &$name;)*
        };
    }

    macro_rules! _read_value {
        ($scanned:expr, ($($t:tt), *)) => {
            ($(_read_value!($scanned, $t)), *)
        };
        ($scanned:expr, [$t:tt; $n:expr]) => {
            (0..$n).map(|_| _read_value!($scanned, $t)).collect::<Vec<_>>()
        };
        ($scanned:expr, _bytes) => {
            _read_value!($scanned, String).into_bytes()
        };
        ($scanned:expr, _index) => {
            _read_value!($scanned, usize) - 1
        };
        ($scanned:expr, $t:ty) => {
            $scanned.next::<$t>()
        };
    }

    #[derive(Default)]
    pub struct Scanned {
        buf: Vec<u8>,
        pos: usize,
    }

    impl Scanned {
        pub fn new<R: Read>(mut input: R, estimated: usize) -> Self {
            let mut buf = Vec::with_capacity(estimated);
            let _ = io::copy(&mut input, &mut buf).unwrap();
            // if buf.last() != Some(&b'\n') {
            //     buf.push(b'\n');
            // }
            // assert!(buf.iter().all(|&b| b <= 0x7f));
            Scanned { buf: buf, pos: 0 }
        }

        #[inline]
        pub fn next<T: FromStr>(&mut self) -> T
        where
            T::Err: fmt::Debug,
        {
            let mut start = None;
            loop {
                match (self.buf[self.pos], start.is_some()) {
                    (b' ', true) | (b'\n', true) => break,
                    (_, true) | (b' ', false) | (b'\n', false) => self.pos += 1,
                    (_, false) => start = Some(self.pos),
                }
            }
            let target = &self.buf[start.unwrap()..self.pos];
            unsafe { str::from_utf8_unchecked(target) }.parse().unwrap()
        }
    }
}

#[allow(dead_code)]
mod output {
    use std::io::{self, BufWriter, StdoutLock, Write as _Write};

    pub fn with_stdout<F: FnMut(&mut BufWriter<StdoutLock>)>(mut f: F) {
        let stdout = io::stdout();
        let mut stdout = BufWriter::new(stdout.lock());
        f(&mut stdout);
        stdout.flush().unwrap();
    }
}

use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
use std::io::Write;
use std::ops::{
    Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
    Mul, MulAssign, Neg, Not, Rem, RemAssign, Sub, SubAssign,
};
use std::str::{self, FromStr};
use std::{char, cmp, f32, f64, fmt, i16, i32, i64, i8, thread, u16, u32, u64, u8};

fn main() {
    input! {
        n: usize,
        s: usize,
        xs: [usize; n],
    }
    if n == 1 {
        return println!("{}", dist(s, xs[0]));
    }
    let mut xs = xs;
    xs.sort();
    let xs = xs;
    let k1 = {
        let mut k1 = xs[1] - xs[0];
        for i in 0..n - 1 {
            k1 = gcd(k1, xs[i + 1] - xs[i]);
        }
        k1
    };
    let (k2, k3) = {
        let (mut k2, mut k3) = (None, 0);
        for &x in &xs {
            if x < s {
                k2 = Some(dist(s, x));
            } else {
                k3 = dist(s, x);
                break;
            }
        }
        (k2, k3)
    };
    match k2 {
        Some(k2) => println!("{}", cmp::max(gcd(k1, k2), gcd(k1, k3))),
        None => println!("{}", gcd(k1, k3)),
    }
}

fn dist(a: usize, b: usize) -> usize {
    cmp::max(a, b) - cmp::min(a, b)
}

fn gcd(a: usize, b: usize) -> usize {
    if a < b {
        gcd(b, a)
    } else if b == 0 {
        a
    } else {
        gcd(b, a % b)
    }
}


Measured memory_bytes: 6396