#![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 mut _scanned = ::_input::Scanned::new(::std::io::stdin(), 1024);
            $(
                let $name = _read_value!(_scanned, $t);
            )*
        };
    }

    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, _1based) => {
            _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');
            }
            debug_assert!(str::from_utf8(&buf_).is_ok());
            debug_assert!(buf_.iter().all(|&c| u32::from(c) <= 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()
        }
    }
}

use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
use std::io::{self, BufWriter, Read, Stderr, StderrLock, Stdout, StdoutLock, Write};
use std::num::{ParseFloatError, ParseIntError};
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, mem, thread, u16, u32, u64, u8};

fn main() {
    input! {
        n: usize,
        k: u64,
        xs: [u64; n],
    }
    let l = 64 - k.leading_zeros() as usize;
    let t = cmp::max(l, 1) - 1;
    let mut zs = vec![0; 64];
    let mut os = vec![0; 64];
    for &x in &xs {
        for i in 0..64 {
            if ((x >> i) & 0x1) == 1 {
                os[i] += 1;
            } else {
                zs[i] += 1;
            }
        }
    }

    let r1 = if k == 0 {
        os.iter().enumerate().map(|(i, &o)| o << i).sum::<u64>()
    } else {
        (0..t + 1)
            .map(|i| {
                (if (k >> i) & 0x1 == 1 {
                    cmp::max(zs[i], os[i])
                } else {
                    os[i]
                }) << i
            })
            .sum::<u64>()
            + (t + 1..64).map(|i| os[i] << i).sum::<u64>()
    };
    let r2 = {
        let mut r2 = os.iter().enumerate().map(|(i, &o)| o << i).sum::<u64>();
        for i in 0..t + 1 {
            if k >> i & 1 == 1 {
                let c = (0..i).map(|j| cmp::max(zs[j], os[j]) << j).sum::<u64>()
                    + (os[i] << i)
                    + (i + 1..t + 1)
                        .map(|j| if (k >> j) & 1 == 1 { zs[j] } else { os[j] } << j)
                        .sum::<u64>()
                    + (t + 1..64).map(|j| os[j] << j).sum::<u64>();
                r2 = cmp::max(r2, c);
            }
        }
        r2
    };
    println!("{}", cmp::max(r1, r2));
}


Measured memory_bytes: 6396