import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 61 - 1
mod = 998244353
import heapq
class Heap():
    def __init__(self, maxi = False):
        self.sum = 0
        self.al = []
        self.maxi = maxi
        self.len = 0

    def __len__(self):
        return len(self.al)

    def add(self, x):
        if self.maxi:
            heapq.heappush(self.al, -x)
        else:
            heapq.heappush(self.al, x)
    
    def pop(self):
        if self.maxi:
            now = heapq.heappop(self.al)
            return -now
        else:
            now = heapq.heappop(self.al)
            return now

    def top(self):
        now = self.pop()
        self.add(now)
        return now
h, w = mi()
a = [li() for _ in range(h)]

zero = Heap()
one = Heap()

color = [[-1] * w for _ in range(h)]


zero.add((a[0][0], 0, 0))
one.add((a[h - 1][w - 1], h - 1, w - 1))
i = 0
while True:
    if i % 2 == 0:
        now, x, y = zero.pop()
    else:
        now, x, y = one.pop()
    if color[x][y] != -1:
        continue
    color[x][y] = i % 2
    f = True
    for tox, toy in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
        nx, ny = x + tox, y + toy
        if 0 <= nx < h and 0 <= ny < w and color[nx][ny] == -1:
            if i % 2 == 0:
                zero.add((a[nx][ny], nx, ny))
            else:
                one.add((a[nx][ny], nx, ny))
        elif 0 <= nx < h and 0 <= ny < w and color[nx][ny] == 1 - color[x][y] and color[nx][ny] != -1:
            f = False
            break
    i += 1
    if not f:
        break
print(i - 2)