use std::cmp::*;
use input_mcr::*;
use std::collections::BinaryHeap;

fn main() {
    input! {
        h: usize,
        w: usize,
        from: (usize1,usize1),
        to: (usize1,usize1),
        field: [chars; h],
    }
    let inf = 1i64 << 50;
    let mut dist = vec![vec![inf; w]; h];
    dist[from.0][from.1] = 0;
    let mut q = BinaryHeap::new();
    q.push((0, from));
    while let Some((d, (y,x))) = q.pop() {
        let d = -d;
        for dy in -2..=2 {
            for dx in -2..=2 {
                let y2 = y as i64 + dy;
                let x2 = x as i64 + dx;
                if ! (0 <= x2 && x2 < w as i64) {
                    continue;
                }
                if ! (0 <= y2 && y2 < h as i64) {
                    continue;
                }
                let y2 = y2 as usize;
                let x2 = x2 as usize;
                if field[y2][x2] == '#' {
                    continue;
                }
                if dist[y2][x2] > d + 1 {
                    dist[y2][x2] = d + 1;
                    let d2 = d + 1;
                    q.push((-d2, (y2,x2)));
                }
            }
        }
        for &(dy,dx) in &[(1,0), (0, 1), (-1,0), (0, -1)] {
            let y2 = y as i64 + dy;
            let x2 = x as i64 + dx;
            if ! (0 <= x2 && x2 < w as i64) {
                continue;
            }
            if ! (0 <= y2 && y2 < h as i64) {
                continue;
            }
            let y2 = y2 as usize;
            let x2 = x2 as usize;
            if field[y2][x2] == '#' {
                continue;
            }
            if dist[y2][x2] > d {
                dist[y2][x2] = d;
                let d2 = d;
                q.push((-d2, (y2,x2)));
            }
        }
    }
    if dist[to.0][to.1] >= inf / 2 {
        println!("-1");
    } else {
        let res = dist[to.0][to.1];
        println!("{}", res);
    }
}

pub mod input_mcr {
    // ref: tanakh <https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8>
    #[macro_export(local_inner_macros)]
    macro_rules! input {
        (source = $s:expr, $($r:tt)*) => {
            let mut parser = Parser::from_str($s);
            input_inner!{parser, $($r)*}
        };
        (parser = $parser:ident, $($r:tt)*) => {
            input_inner!{$parser, $($r)*}
        };
        (new_stdin_parser = $parser:ident, $($r:tt)*) => {
            let stdin = std::io::stdin();
            let reader = std::io::BufReader::new(stdin.lock());
            let mut $parser = Parser::new(reader);
            input_inner!{$parser, $($r)*}
        };
        ($($r:tt)*) => {
            input!{new_stdin_parser = parser, $($r)*}
        };
    }
    
    #[macro_export(local_inner_macros)]
    macro_rules! input_inner {
        ($parser:ident) => {};
        ($parser:ident, ) => {};
        ($parser:ident, $var:ident : $t:tt $($r:tt)*) => {
            let $var = read_value!($parser, $t);
            input_inner!{$parser $($r)*}
        };
    }
    
    #[macro_export(local_inner_macros)]
    macro_rules! read_value {
        ($parser:ident, ( $($t:tt),* )) => {
            ( $(read_value!($parser, $t)),* )
        };
        ($parser:ident, [ $t:tt ; $len:expr ]) => {
            (0..$len).map(|_| read_value!($parser, $t)).collect::<Vec<_>>()
        };
        ($parser:ident, chars) => {
            read_value!($parser, String).chars().collect::<Vec<char>>()
        };
        ($parser:ident, char_) => {
            read_value!($parser, String).chars().collect::<Vec<char>>()[0]
        };
        ($parser:ident, usize1) => {
            read_value!($parser, usize) - 1
        };
        ($parser:ident, line) => {
            $parser.next_line()
        };
        ($parser:ident, line_) => {
            $parser.next_line().chars().collect::<Vec<char>>()
        };
        ($parser:ident, $t:ty) => {
            $parser.next::<$t>().expect("Parse error")
        };
    }
    
    use std::io;
    use std::io::BufRead;
    use std::str;
    use std::collections::VecDeque;
    
    pub struct Parser<R> {
        pub reader: R,
        buf: VecDeque<u8>,
        parse_buf: Vec<u8>,
    }
    
    impl Parser<io::Empty> {
        pub fn from_str(s: &str) -> Parser<io::Empty> {
            Parser {
                reader: io::empty(),
                buf: VecDeque::from(s.as_bytes().to_vec()),
                parse_buf: vec![],
            }
        }
    }
    
    impl<R: BufRead> Parser<R> {
        pub fn new(reader: R) -> Parser<R> {
            Parser {
                reader: reader,
                buf: VecDeque::new(),
                parse_buf: vec![],
            }
        }
        pub fn update_buf(&mut self) {
            loop {
                let (len, complete) = {
                    let buf2 = self.reader.fill_buf().unwrap();
                    self.buf.extend(buf2.iter());
                    let len = buf2.len();
                    (len, buf2.last() < Some(&0x20))
                };
                self.reader.consume(len);
                if complete {
                    break;
                }
            }
        }
        pub fn next<T: str::FromStr>(&mut self) -> Result<T, T::Err> {
            loop {
                while let Some(c) = self.buf.pop_front() {
                    if c > 0x20 {
                        self.buf.push_front(c);
                        break;
                    }
                }
                self.parse_buf.clear();
                while let Some(c) = self.buf.pop_front() {
                    if c <= 0x20 {
                        self.buf.push_front(c);
                        break;
                    } else {
                        self.parse_buf.push(c);
                    }
                }
                if self.parse_buf.is_empty() {
                    self.update_buf();
                } else {
                    return unsafe { str::from_utf8_unchecked(&self.parse_buf) }.parse::<T>();
                }
            }
        }
        pub fn next_line(&mut self) -> String {
            loop {
                while let Some(c) = self.buf.pop_front() {
                    if c >= 0x20 {
                        self.buf.push_front(c);
                        break;
                    }
                }
                self.parse_buf.clear();
                while let Some(c) = self.buf.pop_front() {
                    if c < 0x20 {
                        self.buf.push_front(c);
                        break;
                    } else {
                        self.parse_buf.push(c);
                    }
                }
                if self.parse_buf.is_empty() {
                    self.update_buf();
                } else {
                    return unsafe { str::from_utf8_unchecked(&self.parse_buf) }.to_string();
                }
            }
        }
    }
}



Measured memory_bytes: 15284