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)*}
    };

    ($next:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($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, [ $t:tt ]) => {
        {
            let len = read_value!($next, usize);
            (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:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

#[allow(unused_imports)]
use std::cmp::{min, max};

fn main() {
    input!{
        n: usize,
        m: usize,
        r: [usize; n],
        g: [usize; m]
    }
    let d = 1000000007;
    let mut pos = vec![];
    let mut ys = vec![0];
    let mut i = 0;
    for &x in &r {
        if x < g[0] || x > g[m - 1] {
            continue;
        }
        while g[i + 1] < x {
            i += 1;
        }
        pos.push((x - g[i], g[i + 1] - x));
        ys.push(g[i + 1] - x);
    }
    pos.sort_by(|x, y| if x.0 == y.0 {y.1.cmp(&x.1)} else {x.0.cmp(&y.0)});
    pos.dedup();
    ys.sort();
    ys.dedup();
    let mut bit = BIT::new(ys.len());
    bit.add(0, 1, d);
    for &(_, y) in &pos {
        let idx = ys.binary_search(&y).unwrap();
        let s = bit.sum(idx - 1, d);
        bit.add(idx, s, d);
    }
    println!("{}", bit.sum(ys.len() - 1, d));
}

struct BIT {
    v: Vec<usize>,
    n: usize
}

impl BIT {
    fn new(n: usize) -> BIT {
        BIT{v: vec![0; n + 1], n: n}
    }

    // add x to i th element
    fn add(&mut self, i: usize, x: usize, d: usize) {
        let mut id = i as i64 + 1;
        while id <= self.n as i64 {
            self.v[id as usize] = (self.v[id as usize] + x) % d;
            id += id & -id;
        }
    }

    // sum up to i th element
    fn sum(&self, i: usize, d: usize) -> usize {
        let mut id = i + 1;
        let mut ret = 0;
        while id > 0 {
            ret = (ret + self.v[id]) % d;
            id &= id - 1;
        }
        ret
    }
}


Measured memory_bytes: 12540