#![allow(unused_imports)]
//use itertools::{iproduct, Itertools};
use proconio::input;
use proconio::marker::*;
use std::cmp::Reverse;
use std::collections::*;

fn main() {
    input! {
        h:usize,
        w:usize,
        a:[[usize;w];h],
    }

    let mut pq = [BinaryHeap::new(), BinaryHeap::new()];
    let mut seen = [vec![vec![false; w]; h], vec![vec![false; w]; h]];
    seen[1][0][0] = true;
    seen[0][h - 1][w - 1] = true;
    for Pos { x, y } in Pos::new(0, 0).neigh4(h, w) {
        pq[1].push(Reverse((a[x][y], x, y)));
        seen[1][x][y] = true;
    }
    for Pos { x, y } in Pos::new(h - 1, w - 1).neigh4(h, w) {
        pq[0].push(Reverse((a[x][y], x, y)));
        seen[0][x][y] = true;
    }

    let mut ans = 0;
    let mut mod2 = 1;
    let mut colors = vec![vec![2; w]; h];
    colors[0][0] = 1;
    colors[h - 1][w - 1] = 0;
    while let Some(Reverse((_, x, y))) = pq[mod2].pop() {
        if colors[x][y] != 2 {
            continue;
        }
        ans += 1;
        colors[x][y] = mod2;
        if Pos::new(x, y)
            .neigh4(h, w)
            .any(|Pos { x: nx, y: ny }| colors[nx][ny] == 1 - mod2)
        {
            break;
        }

        for Pos { x: nx, y: ny } in Pos::new(x, y).neigh4(h, w) {
            if seen[mod2][nx][ny] {
                continue;
            }

            pq[mod2].push(Reverse((a[nx][ny], nx, ny)));
            seen[mod2][nx][ny] = true;
        }

        mod2 = 1 - mod2;
    }

    println!("{}", ans);
}

use grid_mgr::*;
mod grid_mgr {
    //[R,D,L,U]
    pub const DIR4: [(usize, usize); 4] = [(0, 1), (1, 0), (0, !0), (!0, 0)];
    pub const DIR8: [(usize, usize); 8] = [
        (1, 0),
        (1, !0),
        (0, !0),
        (!0, !0),
        (!0, 0),
        (!0, 1),
        (0, 1),
        (1, 1),
    ];

    pub struct Pos {
        pub x: usize,
        pub y: usize,
    }

    impl Pos {
        #[allow(dead_code)]
        pub fn new(x: usize, y: usize) -> Self {
            Self { x, y }
        }

        #[allow(dead_code)]
        pub fn neigh4<'a>(&'a self, h: usize, w: usize) -> impl Iterator<Item = Pos> + 'a {
            DIR4.iter().filter_map(move |&(dx, dy)| {
                let nx = self.x.wrapping_add(dx);
                let ny = self.y.wrapping_add(dy);
                if nx < h && ny < w {
                    Some(Pos::new(nx, ny))
                } else {
                    None
                }
            })
        }

        #[allow(dead_code)]
        pub fn neigh8<'a>(&'a self, h: usize, w: usize) -> impl Iterator<Item = Pos> + 'a {
            DIR8.iter().filter_map(move |&(dx, dy)| {
                let nx = self.x.wrapping_add(dx);
                let ny = self.y.wrapping_add(dy);
                if nx < h && ny < w {
                    Some(Pos::new(nx, ny))
                } else {
                    None
                }
            })
        }

        #[allow(dead_code)]
        pub fn line<'a>(
            &'a self,
            h: usize,
            w: usize,
            dir: (usize, usize),
        ) -> impl Iterator<Item = Pos> + 'a {
            (0..).map_while(move |i| {
                let nx = self.x.wrapping_add(dir.0.wrapping_mul(i));
                let ny = self.y.wrapping_add(dir.1.wrapping_mul(i));
                if nx < h && ny < w {
                    Some(Pos::new(nx, ny))
                } else {
                    None
                }
            })
        }

        #[allow(dead_code)]
        pub fn _moveto(&self, h: usize, w: usize, dir: (usize, usize)) -> Option<Pos> {
            let nx = self.x.wrapping_add(dir.0);
            let ny = self.y.wrapping_add(dir.1);
            if nx < h && ny < w {
                Some(Pos::new(nx, ny))
            } else {
                None
            }
        }

        #[allow(dead_code)]
        pub fn moveto(&self, h: usize, w: usize, dir: char) -> Option<Pos> {
            match dir {
                'R' => self._moveto(h, w, DIR4[0]),
                'D' => self._moveto(h, w, DIR4[1]),
                'L' => self._moveto(h, w, DIR4[2]),
                'U' => self._moveto(h, w, DIR4[3]),
                _ => unreachable!(),
            }
        }
    }
}