#![allow(unused)]
// use itertools::Itertools;
use proconio::*;
use std::{cmp::Reverse, collections::*, sync::{mpsc::RecvTimeoutError, BarrierWaitResult}};
const DIJ4: [(usize, usize); 4] = [(0, !0), (!0, 0), (0, 1), (1, 0)];
fn main() {
    input! {
        h: usize, w: usize,
        a: [[usize; w]; h]
    }
    let mut one_heap = BinaryHeap::new();
    let mut zero_heap = BinaryHeap::new();
    let mut one_seen = HashSet::new();
    let mut zero_seen = HashSet::new();
    let nv = nvs(0, 0, h, w);
    for (ni, nj) in nv {
        one_heap.push(Reverse((a[ni][nj], ni, nj)));
    }
    let nv = nvs(h-1, w-1, h, w);
    for (ni, nj) in nv {
        zero_heap.push(Reverse((a[ni][nj], ni, nj)));
    }
    one_seen.insert((0, 0));
    zero_seen.insert((h-1, w-1));

    for t in 0..h*w {
        let mut ok = true;
        if t%2 == 0 {
            let Reverse((_, i, j)) = one_heap.pop().unwrap();
            one_seen.insert((i, j));
            let nvs = nvs(i, j, h, w);
            for (ni, nj) in &nvs {
                if zero_seen.contains(&(*ni, *nj)) {
                    ok = false;
                    break;
                }
            }
            for (ni, nj) in nvs {
                if one_seen.contains(&(ni, nj)) {
                    continue;
                }
                one_heap.push(Reverse((a[ni][nj], ni, nj)));
            }
        }
        else {
            let Reverse((_, i, j)) = zero_heap.pop().unwrap();
            zero_seen.insert((i, j));
            let nvs = nvs(i, j, h, w);
            for (ni, nj) in &nvs {
                if one_seen.contains(&(*ni, *nj)) {
                    ok = false;
                    break;
                }
            }
            for (ni, nj) in nvs {
                if zero_seen.contains(&(ni, nj)) {
                    continue;
                }
                zero_heap.push(Reverse((a[ni][nj], ni, nj)))
            }
        }
        if !ok {
            println!("{}", t+1);
            return;
        }
    }
}

fn nvs(i: usize, j: usize, h: usize, w: usize) -> Vec<(usize, usize)> {
    let mut ret = vec![];
    for (di, dj) in DIJ4 {
        let ni = i.wrapping_add(di);
        let nj = j.wrapping_add(dj);
        if !(ni < h && nj < w) {
            continue;
        }
        ret.push((ni, nj))
    }
    ret
}