from heapq import *
H, W = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(H)]
q = [[], []]
C = [[[-1] * W for _ in range(H)] for _ in range(2)]
B = [[[0] * W for _ in range(H)] for _ in range(2)]
heappush(q[1], (A[0][0], 0, 0))
heappush(q[0], (A[H - 1][W - 1], H - 1, W - 1))
B[1][0][0] = 1
B[0][H - 1][W - 1] = 1
for k in range(1, H * W + 1):
	_, i, j = heappop(q[k % 2])
	C[k % 2][i][j] = 0
	for dx, dy in [(-1, 0), (0, -1), (1, 0), (0, 1)]:
		x = i + dx
		y = j + dy
		if 0 <= x < H and 0 <= y < W:
			if C[1 - k % 2][x][y] == 0:
				exit(print(k - 2))
			if B[k % 2][x][y] == 0:
				heappush(q[k % 2], (A[x][y], x, y))
				B[k % 2][x][y] = 1