H,W = map(int,input().split())
A = [list(map(int,input().split())) for _ in range(H)]

dat = [[-1] * W for _ in range(H)]
#dat[0][0] = 1
#dat[-1][-1] = 0

import heapq
import sys

o = [(A[0][0],0,0)]
e = [(A[-1][-1],H-1,W-1)]

ans = 0
for _ in range(1,H * W+1):
    
    if _ % 2 == 0:
        q = e
        j = 0
    else:
        q = o
        j = 1
    while q:
        a,x,y = heapq.heappop(q)
        if dat[x][y] != -1:continue
        else:break
    dat[x][y] = j
    #print(x,y)
    ans += 1
    for u,v in [(0,-1),(0,1),(1,0),(-1,0)]:
        if 0 <= x + u < H and 0 <= y + v < W:
            k = dat[x + u][y + v]
            if k == 1 - j:
                print(ans - 2)
                exit()
            elif k == -1:
                heapq.heappush(q,(A[x + u][y + v],x + u,y + v))