Problem:
Score : 1200 points

Problem Statement

There are 2N balls in the xy-plane. The coordinates of the i-th of them is (x_i, y_i).
Here, x_i and y_i are integers between 1 and N (inclusive) for all i, and no two balls occupy the same coordinates.

In order to collect these balls, Snuke prepared 2N robots, N of type A and N of type B.
Then, he placed the type-A robots at coordinates (1, 0), (2, 0), ..., (N, 0), and the type-B robots at coordinates (0, 1), (0, 2), ..., (0, N), one at each position.

When activated, each type of robot will operate as follows.

When a type-A robot is activated at coordinates (a, 0), it will move to the position of the ball with the lowest y-coordinate among the balls on the line x = a, collect the ball and deactivate itself. If there is no such ball, it will just deactivate itself without doing anything.

When a type-B robot is activated at coordinates (0, b), it will move to the position of the ball with the lowest x-coordinate among the balls on the line y = b, collect the ball and deactivate itself. If there is no such ball, it will just deactivate itself without doing anything.

Once deactivated, a robot cannot be activated again. Also, while a robot is operating, no new robot can be activated until the operating robot is deactivated.

When Snuke was about to activate a robot, he noticed that he may fail to collect all the balls, depending on the order of activating the robots.

Among the (2N)! possible orders of activating the robots, find the number of the ones such that all the balls can be collected, modulo 1 000 000 007.

Constraints

2 \leq N \leq 10^5

1 \leq x_i \leq N

1 \leq y_i \leq N

If i ≠ j, either x_i ≠ x_j or y_i ≠ y_j.

Inputs

Input is given from Standard Input in the following format:

N
x_1 y_1
...
x_{2N} y_{2N}

Outputs

Print the number of the orders of activating the robots such that all the balls can be collected, modulo 1 000 000 007.

Sample Input 1

2
1 1
1 2
2 1
2 2

Sample Output 1

8

We will refer to the robots placed at (1, 0) and (2, 0) as A1 and A2, respectively, and the robots placed at (0, 1) and (0, 2) as B1 and B2, respectively.
There are eight orders of activation that satisfy the condition, as follows:

A1, B1, A2, B2

A1, B1, B2, A2

A1, B2, B1, A2

A2, B1, A1, B2

B1, A1, B2, A2

B1, A1, A2, B2

B1, A2, A1, B2

B2, A1, B1, A2

Thus, the output should be 8.

Sample Input 2

4
3 2
1 2
4 1
4 2
2 2
4 4
2 1
1 3

Sample Output 2

7392

Sample Input 3

4
1 1
2 2
3 3
4 4
1 2
2 1
3 4
4 3

Sample Output 3

4480

Sample Input 4

8
6 2
5 1
6 8
7 8
6 5
5 7
4 3
1 4
7 6
8 3
2 8
3 6
3 2
8 5
1 5
5 8

Sample Output 4

82060779

Sample Input 5

3
1 1
1 2
1 3
2 1
2 2
2 3

Sample Output 5

0

When there is no order of activation that satisfies the condition, the output should be 0.

Solution in Rust (1.15.1) (judge verdict: Wrong Answer)

#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
use std::io::{Write, BufWriter};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, [ $t:tt ]) => {{
        let len = read_value!($next, usize);
        (0..len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    }};

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

/// Verified by: https://atcoder.jp/contests/pakencamp-2018-day3/submissions/3878249
mod mod_int {
    use std::ops::*;
    pub trait Mod: Copy + Clone { fn m() -> i64; }
    #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord)]
    pub struct ModInt<M> { pub x: i64, phantom: ::std::marker::PhantomData<*const M> }
    impl<M: Mod> ModInt<M> {
        fn check_integrity(self) {
            debug_assert!(self.x >= 0);
            debug_assert!(self.x < M::m());
        }
        // x >= 0
        pub fn new(x: i64) -> Self { ModInt::new_internal(x % M::m()) }
        fn new_internal(x: i64) -> Self {
            ModInt { x: x, phantom: ::std::marker::PhantomData }
        }
        #[allow(dead_code)]
        pub fn mul_fast(self, other: Self) -> Self {
            self.check_integrity();
            other.check_integrity();
            ModInt::new_internal(self.x * other.x % M::m())
        }
        #[allow(dead_code)]
        pub fn mul_slow(self, other: Self) -> Self {
            // Naive multiplication in order to avoid overflow
            self.check_integrity();
            other.check_integrity();
            let mut sum = ModInt::new_internal(0);
            let mut cur = self;
            let mut e = other.x;
            if self.x < other.x {
                cur = other;
                e = self.x;
            }
            while e > 0 {
                if e % 2 == 1 { sum += cur; }
                cur += cur;
                e /= 2;
            }
            sum
        }
        pub fn pow(self, mut e: i64) -> Self {
            self.check_integrity();
            debug_assert!(e >= 0);
            let mut sum = ModInt::new_internal(1);
            let mut cur = self;
            while e > 0 {
                if e % 2 != 0 { sum *= cur; }
                cur *= cur;
                e /= 2;
            }
            sum
        }
        #[allow(dead_code)]
        pub fn inv(self) -> Self { self.pow(M::m() - 2) }
    }
    impl<M: Mod> Add for ModInt<M> {
        type Output = Self;
        fn add(self, other: Self) -> Self {
            self.check_integrity();
            other.check_integrity();
            let mut sum = self.x + other.x;
            if sum >= M::m() { sum -= M::m(); }
            ModInt::new_internal(sum)
        }
    }
    impl<M: Mod> Sub for ModInt<M> {
        type Output = Self;
        fn sub(self, other: Self) -> Self {
            self.check_integrity();
            other.check_integrity();
            let mut sum = self.x - other.x;
            if sum < 0 { sum += M::m(); }
            ModInt::new_internal(sum)
        }
    }
    impl<M: Mod> Mul for ModInt<M> {
        type Output = Self;
        fn mul(self, other: Self) -> Self { self.mul_fast(other) }
    }
    impl<M: Mod> AddAssign for ModInt<M> {
        fn add_assign(&mut self, other: Self) { *self = *self + other; }
    }
    impl<M: Mod> SubAssign for ModInt<M> {
        fn sub_assign(&mut self, other: Self) { *self = *self - other; }
    }
    impl<M: Mod> MulAssign for ModInt<M> {
        fn mul_assign(&mut self, other: Self) { *self = *self * other; }
    }
    impl<M> ::std::fmt::Display for ModInt<M> {
        fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
            self.x.fmt(f)
        }
    }
    impl<M> ::std::fmt::Debug for ModInt<M> {
        fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
            self.x.fmt(f)
        }
    }
} // mod mod_int

macro_rules! define_mod {
    ($struct_name: ident, $modulo: expr) => {
        #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
        struct $struct_name {}
        impl mod_int::Mod for $struct_name { fn m() -> i64 { $modulo } }
    }
}
const MOD: i64 = 998_244_353;
define_mod!(P, MOD);
type ModInt = mod_int::ModInt<P>;

#[derive(Clone)]
struct BitSet {
    size: usize,
    buf: Vec<usize>,
}

impl BitSet {
    // size should be a multiple of bit-size of usize.
    fn new(size: usize) -> Self {
        let w = 8 * std::mem::size_of::<usize>();
        assert_eq!(size & (w - 1), 0);
        let count = size / w;
        BitSet {
            size: size,
            buf: vec![0; count],
        }
    }
    fn set(&mut self, idx: usize, val: bool) {
        debug_assert!(idx < self.size);
        let w = 8 * std::mem::size_of::<usize>();
        let idx0 = idx / w;
        let idx1 = idx & (w - 1);
        if val {
            self.buf[idx0] |= 1 << idx1;
        } else {
            self.buf[idx0] &= !(1 << idx1);
        }
    }
    fn shl(&self, val: usize) -> Self {
        if val >= self.size { return Self::new(self.size); }
        let w = 8 * std::mem::size_of::<usize>();
        let count = self.size / w;
        let sh0 = val / w;
        let sh1 = val & (w - 1);
        let mut ans = Self::new(self.size);
        if sh1 == 0 {
            for i in 0 .. count - sh0 {
                ans.buf[i + sh0] = self.buf[i];
            }
        } else {
            ans.buf[sh0] = self.buf[0] << sh1;
            for i in 1 .. count - sh0 {
                ans.buf[i + sh0] = self.buf[i] << sh1
                    | self.buf[i - 1] >> (w - sh1);
            }
        }
        ans
    }
    fn shr(&self, val: usize) -> Self {
        if val >= self.size { return Self::new(self.size); }
        let w = 8 * std::mem::size_of::<usize>();
        let count = self.size / w;
        let sh0 = val / w;
        let sh1 = val & (w - 1);
        let mut ans = Self::new(self.size);
        if sh1 == 0 {
            for i in 0 .. count - sh0 {
                ans.buf[i] = self.buf[i + sh0];
            }
        } else {
            for i in 0 .. count - sh0 - 1 {
                ans.buf[i] = self.buf[i + sh0] >> sh1
                    | self.buf[i + sh0 + 1] << (w - sh1);
            }
            ans.buf[self.size - sh0 - 1] = self.buf[self.size - 1] >> sh1;
        }
        ans
    }
    fn msb(&self) -> Option<usize> {
        let w = 8 * std::mem::size_of::<usize>();
        let count = self.size / w;
        for i in (0 .. count).rev() {
            if self.buf[i] != 0 {
                return Some(w * i + w - 1 - self.buf[i].leading_zeros() as usize);
            }
        }
        None
    }
    fn get(&self, idx: usize) -> bool {
        let w = 8 * std::mem::size_of::<usize>();
        debug_assert!(idx < self.size);
        let idx0 = idx / w;
        let idx1 = idx & (w - 1);
        (self.buf[idx0] >> idx1 & 1) == 1
    }
}
impl std::fmt::Display for BitSet {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        let size = match self.msb() {
            None => return f.write_str("0"),
            Some(size) => size + 1,
        };
        for i in (0 .. size).rev() {
            f.write_str(if self.get(i) { "1" } else { "0" })?
        }
        Ok(())
    }
}
impl std::fmt::Debug for BitSet {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        std::fmt::Display::fmt(&self, f)
    }
}

// TODO reference is not allowed as rhs
impl<'a> std::ops::BitXorAssign for BitSet {
    fn bitxor_assign(&mut self, other: BitSet) {
        debug_assert_eq!(self.size, other.size);
        let w = 8 * std::mem::size_of::<usize>();
        let count = self.size / w;
        for i in 0 .. count {
            self.buf[i] ^= other.buf[i];
        }
    }
}

fn gcd(mut a: BitSet, mut b: BitSet) -> BitSet {
    let (mut da, mut db) = match (a.msb(), b.msb()) {
        (None, _) => return b,
        (_, None) => return a,
        (Some(da), Some(db)) => (da, db),
    };
    if da < db {
        std::mem::swap(&mut da, &mut db);
        std::mem::swap(&mut a, &mut b);
    }

    for i in (db .. da + 1).rev() {
        if a.get(i) {
            a ^= b.shl(i - db);
        }
    }
    gcd(b, a)
}

const W: usize = 4032;
fn to_bitset(mut c: Vec<char>) -> BitSet {
    let mut ans = BitSet::new(W);
    c.reverse();
    for i in 0 .. c.len() {
        if c[i] == '1' {
            ans.set(i, true);
        }
    }
    ans
}

fn solve() {
    let out = std::io::stdout();
    let mut out = BufWriter::new(out.lock());
    macro_rules! puts {
        ($($format:tt)*) => (write!(out,$($format)*).unwrap());
    }
    input! {
        n: usize,
        x: chars,
        a: [chars; n],
    }
    let x = to_bitset(x);
    let a: Vec<BitSet> = a.into_iter().map(to_bitset).collect();
    let mut g = to_bitset(vec!['0']);
    for a in a { g = gcd(g, a); }
    let hi = g.msb().unwrap();
    let mut y = to_bitset(vec!['0']);
    let mut r = x.clone();
    // What is the largest multiple of g that is <= x?
    for i in (hi .. W).rev() {
        if r.get(i) {
            r ^= g.shl(i - hi);
            y.set(i - hi, true);
        }
    }
    let mut z = x.clone();
    z ^= r;
    let mut lt = false;
    for i in (0 .. W).rev() {
        if x.get(i) != z.get(i) {
            lt = x.get(i) < z.get(i);
            break;
        }
    }
    let mut tot = ModInt::new(0);
    for i in (hi .. W).rev() {
        tot += tot;
        if z.get(i) {
            tot += ModInt::new(1);
        }
    }
    if !lt {
        tot += ModInt::new(1);
    }
    puts!("{}\n", tot);
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}