#![allow(unused_imports)]

// language: Rust(1.42.0)
// check available crates on AtCoder at "https://atcoder.jp/contests/language-test-202001"
// My Library Repositry is at "https://github.com/Loptall/sfcpl"

/*
    水コーダーになれてうれしいです
*/

// from std...
use std::cmp::{
    max, min, Ordering,
    Ordering::{Equal, Greater, Less},
    Reverse,
};
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, VecDeque};
use std::convert::TryInto;
use std::fmt;
use std::mem::swap;
use std::num::{NonZeroU32, ParseIntError};
use std::ops::{
    Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
    Index, IndexMut, Mul, MulAssign, Neg, Rem, RemAssign, Shl, ShlAssign, Shr, ShrAssign, Sub,
    SubAssign,
};
use std::process::exit;
use std::{f32, f64, i128, i16, i32, i64, i8, isize, u128, u16, u32, u64, u8, usize};

// Dep' crates are...
use itertools::*;
use itertools_num::*;
use lazy_static::lazy_static;
use maplit::{btreemap, btreeset, hashmap, hashset};
use num_bigint::{BigInt, BigUint};
use num_complex::Complex;
use num_integer::{binomial, gcd, lcm, multinomial, Integer};
use num_rational::Rational;
use num_traits::{
    clamp, one, pow, zero, Num, NumAssignOps, NumOps, One, Pow, Signed, Unsigned, Zero,
};
use permutohedron::Heap;
use proconio::{
    derive_readable, fastout, input, is_stdin_empty,
    marker::{Bytes, Chars, Isize1, Usize1},
};
use rand::random;

pub trait Visualize {
    fn visualize(&self, split: &str);
    fn continuous(&self) {
        self.visualize("");
    }
    fn spaces(&self) {
        self.visualize(" ");
    }
    fn lines(&self) {
        self.visualize("\n");
    }
}
macro_rules! impl_vis_for_sized {
    ($($t:ty),+) => {
        $(
            impl Visualize for $t {
                fn visualize(&self, _split: &str) {
                    print!("{}", self);
                }
            }
        )+
    };
}
impl_vis_for_sized! {
    usize, u8, u16, u32, u64, u128,
    isize, i8, i16, i32, i64, i128,
    f64, f32,
    String, &str, char
}
impl<T: fmt::Display> Visualize for [T] {
    fn visualize(&self, split: &str) {
        print!("{}", self.iter().join(split));
    }
}
#[macro_export]
macro_rules! vis {
    // end
    () => {
        println!();
    };

    // last element + trailing pattern
    ($last:expr ;) => {
        $last.lines();
        vis!()
    };
    ($last:expr =>) => {
        $last.continuous();
        vis!();
    };
    ($last:expr $(,)?) => {
        $last.spaces();
        vis!();
    };

    // get first element and pass rest
    ($first:expr; $($rest:tt)*) => {
        $first.lines();
        println!();
        vis!($($rest)*);
    };
    ($first:expr => $($rest:tt)*) => {
        $first.continuous();
        vis!($($rest)*);
    };
    ($first:expr, $($rest:tt)*) => {
        $first.spaces();
        print!(" ");
        vis!($($rest)*);
    };
}
pub const MOD10E9_7: usize = 1000000007; // 10 ^ 9 + 7
pub const MOD99_: usize = 998244353;
pub const MAX: usize = std::usize::MAX; // = 2 ^ 64 - 1 = 18446744073709551615 ≈ 1.8 * 10 ^ 19
pub const INF: usize = 2000000000000000000; // MAX / 9 < 2 * 10e18 < MAX / 10
pub const FNI: i64 = -2000000000000000000; // == -(INF as i64)
pub const PI: f64 = f64::consts::PI; // 3.141592653589793 -- 10 ^ -15
pub const ASCII_A_LARGE: u8 = 65;
pub const ASCII_A_SMALL: u8 = 97;
pub const ASCII_0: u8 = 48;
pub const ADJ4: &[(isize, isize); 4] = &[(1, 0), (0, 1), (-1, 0), (0, -1)];
pub const ADJ8: &[(isize, isize); 8] = &[
    (1, 0),
    (1, 1),
    (0, 1),
    (-1, 1),
    (-1, 0),
    (-1, -1),
    (0, -1),
    (1, -1),
];

// code...
// #[fastout]
fn main() {
    input! {
        h: usize, w: usize,
        start: (Usize1, Usize1),
        goal: (Usize1, Usize1),
        board: [Chars; h]
    }

    let mut d = vec![vec![INF; w]; h];
    d[start.0][start.1] = 0;

    let mut q = BinaryHeap::new();
    q.push((Reverse(0), start.0, start.1));

    while !q.is_empty() {
        // (x, y, ワープを使った回数)
        let (Reverse(warped), x, y) = q.pop().unwrap();

        if (x, y) == goal {
            vis!(warped);
            return;
        }

        for &(dx, dy) in ADJ4 {
            if (x as isize + dx) >= 0
                && (x as isize + dx) < h as isize
                && (y as isize + dy) >= 0
                && (y as isize + dy) < w as isize
                && board[(x as isize + dx) as usize][(y as isize + dy) as usize] == '.'
                && d[(x as isize + dx) as usize][(y as isize + dy) as usize] > warped
            {
                d[(x as isize + dx) as usize][(y as isize + dy) as usize] = warped;
                q.push((
                    Reverse(warped),
                    (x as isize + dx) as usize,
                    (y as isize + dy) as usize,
                ));
            }
        }

        for nx in x.saturating_sub(2)..=min(x + 2, h - 1) {
            for ny in y.saturating_sub(2)..=min(y + 2, w - 1) {
                if board[nx][ny] == '.' && d[nx][ny] > warped + 1 {
                    d[nx][ny] = warped + 1;
                    q.push((Reverse(warped + 1), nx, ny));
                }
            }
        }
    }

    let ans = d[goal.0][goal.1];
    vis!(if ans == INF { -1 } else { ans as i64 });
}


Measured memory_bytes: 15112