#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*};
use std::str;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let H = input!(usize);
    let W = input!(usize);

    let A = {
        let mut a = vec![];

        for _ in 0..H {
            let b = input!(usize, W);
            a.push(b);
        }

        a
    };

    let mut pos_inv = std::collections::BTreeMap::new();

    for i in 0..H {
        for j in 0..W {
            pos_inv.insert(A[i][j], (i, j));
        }
    }

    let mut around_1 = std::collections::BTreeSet::new();
    let mut around_0 = std::collections::BTreeSet::new();

    let mut seen = vec![vec![false; W]; H];
    let mut seen1 = vec![vec![false; W]; H];
    let mut seen0 = vec![vec![false; W]; H];

    macro_rules! act1 {
        ($y: expr, $x: expr) => {
            if $x > 0 && !seen[$y][$x - 1] {
                around_1.insert(A[$y][$x - 1]);
            }

            if $y > 0 && !seen[$y - 1][$x] {
                around_1.insert(A[$y - 1][$x]);
            }

            if $x + 1 < W && !seen[$y][$x + 1] {
                around_1.insert(A[$y][$x + 1]);
            }

            if $y + 1 < H && !seen[$y + 1][$x] {
                around_1.insert(A[$y + 1][$x]);
            }
        };
    }

    macro_rules! act0 {
        ($y: expr, $x: expr) => {
            if $x > 0 && !seen[$y][$x - 1] {
                around_0.insert(A[$y][$x - 1]);
            }

            if $y > 0 && !seen[$y - 1][$x] {
                around_0.insert(A[$y - 1][$x]);
            }

            if $x + 1 < W && !seen[$y][$x + 1] {
                around_0.insert(A[$y][$x + 1]);
            }

            if $y + 1 < H && !seen[$y + 1][$x] {
                around_0.insert(A[$y + 1][$x]);
            }
        };
    }

    // (0, 0)
    seen[0][0] = true;
    seen1[0][0] = true;
    act1!(0, 0);

    // (H - 1, W - 1)
    seen[H - 1][W - 1] = true;
    seen0[H - 1][W - 1] = true;
    act0!(H - 1, W - 1);

    let mut ans = 0;

    loop {
        if ans % 2 == 0 {
            let m = around_1.range(..).next();

            match m {
                Some(&v) => {
                    ans += 1;

                    around_1.remove(&v);
                    let &(y, x) = pos_inv.get(&v).unwrap();

                    seen[y][x] = true;
                    seen1[y][x] = true;
                    act1!(y, x);

                    if around_0.contains(&v) {
                        around_0.remove(&v);
                    }

                    {
                        if x > 0 && seen0[y][x - 1] {
                            break;
                        }

                        if y > 0 && seen0[y - 1][x] {
                            break;
                        }

                        if x + 1 < W && seen0[y][x + 1] {
                            break;
                        }

                        if y + 1 < H && seen0[y + 1][x] {
                            break;
                        }
                    }
                }
                None => {
                    break;
                }
            }
        } else {
            let m = around_0.range(..).next();

            match m {
                Some(&v) => {
                    ans += 1;

                    around_0.remove(&v);
                    let &(y, x) = pos_inv.get(&v).unwrap();

                    seen[y][x] = true;
                    seen0[y][x] = true;
                    act0!(y, x);

                    if around_1.contains(&v) {
                        around_1.remove(&v);
                    }

                    {
                        if x > 0 && seen1[y][x - 1] {
                            break;
                        }

                        if y > 0 && seen1[y - 1][x] {
                            break;
                        }

                        if x + 1 < W && seen1[y][x + 1] {
                            break;
                        }

                        if y + 1 < H && seen1[y + 1][x] {
                            break;
                        }
                    }
                }
                None => {
                    break;
                }
            }
        }
    }

    writeln!(out, "{}", ans);
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}