import sys
input = sys.stdin.readline

from heapq import heappop,heappush,heapify

H,W=map(int,input().split())

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

Q1=[]
Q2=[]
USE=[[0]*W for i in range(H)]
USE2=[[0]*W for i in range(H)]

USE3=[[0]*W for i in range(H)]
USE4=[[0]*W for i in range(H)]


Q1.append((A[0][1],0,1))
Q1.append((A[1][0],1,0))

Q2.append((A[H-1][W-2],H-1,W-2))
Q2.append((A[H-2][W-1],H-2,W-1))

heapify(Q1)
heapify(Q2)

USE[0][0]=1
USE2[H-1][W-1]=1
flag=0
for tt in range(10**9):
    if flag==1:
        break
    if tt%2==0:
        while True:
            _,x,y=heappop(Q1)
            if USE[x][y]==1:
                continue
            USE[x][y]=1
            break

        for z,w in [(x+1,y),(x-1,y),(x,y-1),(x,y+1)]:
            if 0<=z<H and 0<=w<W:
                if USE3[z][w]==0:
                    heappush(Q1,(A[z][w],z,w))
                    USE3[z][w]=1
                if USE2[z][w]==1:
                    flag=1
    else:
        while True:
            _,x,y=heappop(Q2)
            if USE2[x][y]==1:
                continue
            USE2[x][y]=1
            break


        for z,w in [(x+1,y),(x-1,y),(x,y-1),(x,y+1)]:
            if 0<=z<H and 0<=w<W:
                if USE4[z][w]==0:
                    heappush(Q2,(A[z][w],z,w))
                    USE4[z][w]=1
                if USE[z][w]==1:
                    flag=1
print(tt)