//https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 より
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

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

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };
    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };
    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };
    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };
    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

//

fn run() {
    input! {
        h: usize,
        w: usize,
        s: (usize1, usize1),
        t: (usize1, usize1),
        board: [chars; h],
    }
    let mut dp = vec![vec![std::usize::MAX; w]; h];
    let mut q = std::collections::VecDeque::new();
    dp[s.1][s.0] = 0;
    q.push_back((s.1, s.0));
    while let Some((x, y)) = q.pop_front() {
        for &(a, b) in [(x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)].iter() {
            if a < h && b < w && board[a][b] == '.' && dp[a][b] > dp[x][y] + 1 {
                dp[a][b] = dp[x][y] + 1;
                q.push_back((a, b));
            }
        }
    }
    println!("{}", dp[t.1][t.0]);
}

fn main() {
    run();
}