#[allow(unused_imports)]
use itertools::Itertools;
#[allow(unused_imports)]
use itertools_num::ItertoolsNum;
#[allow(unused_imports)]
use std::cmp;
use std::collections::BinaryHeap;
#[allow(unused_imports)]
use std::iter;
#[allow(unused_imports)]
use superslice::*;

fn run() {
    let (r, w) = (std::io::stdin(), std::io::stdout());
    let mut sc = IO::new(r.lock(), w.lock());

    let h: usize = sc.read();
    let w: usize = sc.read();
    let ch = sc.read::<usize>() - 1;
    let cw = sc.read::<usize>() - 1;
    let dh = sc.read::<usize>() - 1;
    let dw = sc.read::<usize>() - 1;
    let s = sc.read_char_grid(h);

    let next = vec![(-1, 0), (0, -1), (1, 0), (0, 1)];

    let mut queue = BinaryHeap::new();
    let mut dist = vec![vec![-1; w]; h];
    queue.push((0, ch, cw));
    let mut ans = -1;

    while let Some((warp, cur_h, cur_w)) = queue.pop() {
        let warp = -warp;
        if cur_h == dh && cur_w == dw {
            ans = warp;
            break;
        }

        if dist[cur_h][cur_w] >= 0 {
            continue;
        }
        dist[cur_h][cur_w] = warp;

        for &(dy, dx) in next.iter() {
            let ny = cur_h as i64 + dy;
            let nx = cur_w as i64 + dx;
            if ny >= 0 && ny < h as i64 && nx >= 0 && nx < w as i64 {
                if s[ny as usize][nx as usize] == '.' && dist[ny as usize][nx as usize] < 0 {
                    queue.push((-warp, ny as usize, nx as usize));
                }
            }
        }

        for dy in -2..=2 {
            for dx in -2..=2 {
                let ny = cur_h as i64 + dy;
                let nx = cur_w as i64 + dx;
                if ny >= 0 && ny < h as i64 && nx >= 0 && nx < w as i64 {
                    if s[ny as usize][nx as usize] == '.' && dist[ny as usize][nx as usize] < 0 {
                        queue.push((-warp - 1, ny as usize, nx as usize));
                    }
                }
            }
        }
    }

    println!("{}", ans);
}

fn main() {
    std::thread::Builder::new()
        .name("run".into())
        .stack_size(256 * 1024 * 1024)
        .spawn(run)
        .unwrap()
        .join()
        .unwrap();
}

pub struct IO<R, W: std::io::Write>(R, std::io::BufWriter<W>);

impl<R: std::io::Read, W: std::io::Write> IO<R, W> {
    pub fn new(r: R, w: W) -> IO<R, W> {
        IO(r, std::io::BufWriter::new(w))
    }
    pub fn write<S: std::ops::Deref<Target = str>>(&mut self, s: S) {
        use std::io::Write;
        self.1.write(s.as_bytes()).unwrap();
    }
    pub fn read<T: std::str::FromStr>(&mut self) -> T {
        use std::io::Read;
        let buf = self
            .0
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b' ' || b == b'\n' || b == b'\r' || b == b'\t')
            .take_while(|&b| b != b' ' && b != b'\n' && b != b'\r' && b != b'\t')
            .collect::<Vec<_>>();
        unsafe { std::str::from_utf8_unchecked(&buf) }
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn read_vec<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read()).collect()
    }
    pub fn read_pairs<T: std::str::FromStr>(&mut self, n: usize) -> Vec<(T, T)> {
        (0..n).map(|_| (self.read(), self.read())).collect()
    }
    pub fn read_pairs_1_indexed(&mut self, n: usize) -> Vec<(usize, usize)> {
        (0..n)
            .map(|_| (self.read::<usize>() - 1, self.read::<usize>() - 1))
            .collect()
    }
    pub fn read_chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
    pub fn read_char_grid(&mut self, n: usize) -> Vec<Vec<char>> {
        (0..n).map(|_| self.read_chars()).collect()
    }
    pub fn read_matrix<T: std::str::FromStr>(&mut self, n: usize, m: usize) -> Vec<Vec<T>> {
        (0..n)
            .map(|_| (0..m).map(|_| self.read()).collect())
            .collect()
    }
}


Measured memory_bytes: 10612