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

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

dic = {}
lis = []
for i in range(H):
    for j in range(W):
        lis.append( A[i][j] )
lis.sort()
for i in range(len(lis)):
    dic[lis[i]] = i
for i in range(H):
    for j in range(W):
        A[i][j] = dic[A[i][j]]

rev = [0] * (H*W)
for i in range(H):
    for j in range(W):
        rev[A[i][j]] = (i,j)

color = [[-1] * W for i in range(H)]
state = [[0] * W for i in range(H)]

q0 = []
q1 = []

color[0][0] = 1
q1.append( A[0][0] )
color[H-1][W-1] = 0
q0.append( A[H-1][W-1] )


ans = 0

for i in range(H*W+1):

    flag = False
    if i % 2 == 0:

        num = heapq.heappop(q0)
        x,y = rev[num]
        color[x][y] = 0

        for xx,yy in ( (x-1,y),(x+1,y),(x,y-1),(x,y+1) ):
            if not (0 <= xx < H and 0 <= yy < W):
                continue
            if state[xx][yy] & 1 == 0:
                state[xx][yy] |= 1
                heapq.heappush( q0 , A[xx][yy])

            if color[xx][yy] == 1:
                flag = True

    else:

        num = heapq.heappop(q1)
        x,y = rev[num]
        color[x][y] = 1

        for xx,yy in ( (x-1,y),(x+1,y),(x,y-1),(x,y+1) ):
            if not (0 <= xx < H and 0 <= yy < W):
                continue
            if state[xx][yy] & 2 == 0:
                state[xx][yy] |= 2
                heapq.heappush( q1 , A[xx][yy])

            if color[xx][yy] == 0:
                flag = True

    ans += 1
    if flag:
        break

print (ans - 3)