from heapq import *

EMPTY = -1
H, W = map(int, input().split())
nums = [list(map(int, input().split())) for _ in range(H)]
cols = [[EMPTY] * W for _ in range(H)]
cols[0][0] = 0
cols[H - 1][W - 1] = 1

q0 = [(nums[0][1], (0, 1)), (nums[1][0], (1, 0))]
heapify(q0)

q1 = [(nums[H - 1][W - 2], (H - 1, W - 2)), (nums[H - 2][W - 1], (H - 2, W - 1))]
heapify(q1)

Q = [q0, q1]

dirs = [[0, 1], [1, 0], [-1, 0], [0, -1]]
for i in range(0,100):
    i2 = i % 2
    a, (x, y) = heappop(Q[i2])
    if cols[x][y] == EMPTY:
        cols[x][y] = i2
        for xd, yd in dirs:
            x2 = x + xd
            y2 = y + yd
            if 0 <= x2 < H and 0 <= y2 < W:
                if cols[x2][y2] == i2 ^ 1:
                    print(i + 1)
                    exit()
                elif cols[x2][y2] == EMPTY:
                    heappush(Q[i2], (nums[x2][y2], (x2, y2)))