from heapq import heappush, heappop, heapify

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

color = [[-1]*W for _ in range(H)]
color[0][0] = 0
color[H-1][W-1] = 1
que0 = [(A[1][0], 1, 0), (A[0][1], 0, 1)]
color[1][0] = 0
color[0][1] = 0
que1 = [(A[H-2][W-1], H-2, W-1), (A[H-1][W-2], H-1, W-2)]
color[H-2][W-1] = 1
color[H-1][W-2] = 1
B = [[-1]*W for _ in range(H)]
B[0][0] = 0
B[H-1][W-1] = 1
heapify(que0)
heapify(que1)
direction = [(-1,0),(0,1),(1,0),(0,-1)]
cnt = 0
while True:
    if cnt%2 == 0:
        n, h, w = heappop(que0)
    else:
        n, h, w = heappop(que1)
    B[h][w] = cnt%2
    for dh, dw in direction:
        if 0<=h+dh<H and 0<=w+dw<W and color[h+dh][w+dw]==-1:
            color[h+dh][w+dw] = cnt%2
            if cnt%2 == 0:
                heappush(que0, (A[h+dh][w+dw], h+dh, w+dw))
            else:
                heappush(que1, (A[h+dh][w+dw], h+dh, w+dw))
        elif 0<=h+dh<H and 0<=w+dw<W and B[h+dh][w+dw] == (cnt%2)^1:
            exit(print(cnt+1))
    cnt += 1