import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd

h,w = map(int,input().split())
a = [list(map(int,input().split())) for i in range(h)]

col = [[-1]*(w) for i in range(h)]
r = [(a[0][0],0*w+0)]
b = [(a[-1][-1],(h-1)*w+(w-1))]

dx = [1,-1,0,0]
dy = [0,0,1,-1]
for i in range(h*w+10):
    if i % 2 == 0:
        while r:
            num, crr = heappop(r)
            x, y = crr//w, crr%w
            if col[x][y] == -1:
                col[x][y] = 1
                break
        for j in range(4):
            nx = x+dx[j]
            ny = y+dy[j]
            if not (0<=nx<h and 0<=ny<w):continue
            if col[nx][ny] == 0:
                print(i-1)
                exit()
            heappush(r, (a[nx][ny],nx*w+ny))
    else:
        while b:
            num, crr = heappop(b)
            x, y = crr//w, crr%w
            if col[x][y] == -1:
                col[x][y] = 0
                break
        for j in range(4):
            nx = x+dx[j]
            ny = y+dy[j]
            if not (0<=nx<h and 0<=ny<w):continue
            if col[nx][ny] == 1:
                print(i-1)
                exit()
            heappush(b, (a[nx][ny], nx*w+ny))