#![allow(unused_imports)]
#![allow(non_snake_case, unused)]

use std::cmp::*;
use std::collections::*;
use std::ops::*;

// https://atcoder.jp/contests/hokudai-hitachi2019-1/submissions/10518254

macro_rules! eprint {
    ($($t:tt)*) => {{
        use ::std::io::Write;
        let _ = write!(::std::io::stderr(), $($t)*);
    }};
}
macro_rules! eprintln {
    () => { eprintln!(""); };
    ($($t:tt)*) => {{
        use ::std::io::Write;
        let _ = writeln!(::std::io::stderr(), $($t)*);
    }};
}
macro_rules! dbg {
    ($v:expr) => {{
        let val = $v;
        eprintln!("[{}:{}] {} = {:?}", file!(), line!(), stringify!($v), val);
        val
    }}
}

macro_rules! mat {
    ($($e:expr),*) => { Vec::from(vec![$($e),*]) };
    ($($e:expr,)*) => { Vec::from(vec![$($e),*]) };
    ($e:expr; $d:expr) => { Vec::from(vec![$e; $d]) };
    ($e:expr; $d:expr $(; $ds:expr)+) => { Vec::from(vec![mat![$e $(; $ds)*]; $d]) };
}

macro_rules! ok {
    ($a:ident$([$i:expr])*.$f:ident()$(@$t:ident)*) => {
        $a$([$i])*.$f($($t),*)
    };
    ($a:ident$([$i:expr])*.$f:ident($e:expr$(,$es:expr)*)$(@$t:ident)*) => { {
        let t = $e;
        ok!($a$([$i])*.$f($($es),*)$(@$t)*@t)
    } };
}

pub fn readln() -> String {
    let mut line = String::new();
    ::std::io::stdin().read_line(&mut line).unwrap_or_else(|e| panic!("{}", e));
    line
}

macro_rules! read {
    ($($t:tt),*; $n:expr) => {{
        let stdin = ::std::io::stdin();
        let ret = ::std::io::BufRead::lines(stdin.lock()).take($n).map(|line| {
            let line = line.unwrap();
            let mut it = line.split_whitespace();
            _read!(it; $($t),*)
        }).collect::<Vec<_>>();
        ret
    }};
    ($($t:tt),*) => {{
        let line = readln();
        let mut it = line.split_whitespace();
        _read!(it; $($t),*)
    }};
}

macro_rules! _read {
    ($it:ident; [char]) => {
        _read!($it; String).chars().collect::<Vec<_>>()
    };
    ($it:ident; [u8]) => {
        Vec::from(_read!($it; String).into_bytes())
    };
    ($it:ident; usize1) => {
        $it.next().unwrap_or_else(|| panic!("input mismatch")).parse::<usize>().unwrap_or_else(|e| panic!("{}", e)) - 1
    };
    ($it:ident; [usize1]) => {
        $it.map(|s| s.parse::<usize>().unwrap_or_else(|e| panic!("{}", e)) - 1).collect::<Vec<_>>()
    };
    ($it:ident; [$t:ty]) => {
        $it.map(|s| s.parse::<$t>().unwrap_or_else(|e| panic!("{}", e))).collect::<Vec<_>>()
    };
    ($it:ident; $t:ty) => {
        $it.next().unwrap_or_else(|| panic!("input mismatch")).parse::<$t>().unwrap_or_else(|e| panic!("{}", e))
    };
    ($it:ident; $($t:tt),+) => {
        ($(_read!($it; $t)),*)
    };
}


pub fn main() {
    let _ = ::std::thread::Builder::new().name("run".to_string()).stack_size(32 * 1024 * 1024).spawn(run).unwrap().join();
}

const MOD: usize = 1_000_000_007;
const INF: i64 = std::i64::MAX/2;

fn solve() {
    let (h,w) = read!(usize,usize);
    let s = read!(usize,usize);
    let g = read!(usize,usize);
    let c = read!([char];h);
    let mut q = VecDeque::new();
    let mut dist = vec![vec![INF;w];h];
    dist[s.0-1][s.1-1] = 0;
    q.push_front((0,s.0-1,s.1-1));
    while let Some((d,x,y)) = q.pop_front() {
        if dist[x][y] < d {
            continue;
        }
        let dir = [(1,0),(0,1),(-1,0),(0,-1)];
        for (ndir,&(dx,dy)) in dir.iter().enumerate() {
            let nx = x.wrapping_add(dx as usize);
            let ny = y.wrapping_add(dy as usize);
            if nx>=h || ny>=w {
                continue;
            }
            if c[nx][ny]=='#' {
                continue;
            }
            if dist[nx][ny]<= d {
                continue;
            }
            dist[nx][ny] = d;
            q.push_front((d,nx,ny));
        }
        for i in -2..=2 {
            for j in -2..=2 {
                let nx = x.wrapping_add(i as usize);
                let ny = y.wrapping_add(j as usize);
                if nx>=h || ny>=w {
                    continue;
                }
                if c[nx][ny]=='#' {
                    continue;
                }
                if dist[nx][ny]<= d {
                    continue;
                }
                dist[nx][ny] = d+1;
                q.push_back((d+1,nx,ny));
            }
        }
    }
    if dist[g.0-1][g.1-1] == INF {
        println!("-1");
    }
    else {
        println!("{}",dist[g.0-1][g.1-1]);
    }
}

fn run() {
    solve();
}


Measured memory_bytes: 14260