from collections import *

W, H = map(int, input().split())
M = []
for i in range(H):
    M.append(list(map(int, input().split())))

inf = 10 ** 18
dist = defaultdict(lambda:inf)
Q = deque()
if M[1][0] != M[0][0]:
    dist[(1, 0, 0, 0)] = 1
    Q.append([1, 0, 0, 0])
if M[0][1] != M[0][0]:
    dist[(0, 1, 0, 0)] = 1
    Q.append([0, 1, 0, 0])


def kadomatsu(a, b, c):
    S = set([a, b, c])
    if len(S) != 3:
        return False
    if b > a and b > c:
        return True
    if b < a and b < c:
        return True
    return False

dx = [1, 0, -1, 0]
dy = [0, 1, 0, -1]
while Q:
    x, y, px, py = Q.popleft()
    for k in range(4):
        nx = x + dx[k]
        ny = y + dy[k]
        if nx < 0 or nx > H - 1 or ny < 0 or ny > W - 1:
            continue
        if dist[(nx, ny, x, y)] != inf:
            continue
        if kadomatsu(M[px][py], M[x][y], M[nx][ny]):
            dist[(nx, ny, x, y)] = dist[(x, y, px, py)] + 1
            Q.append([nx, ny, x, y])

ans = min(dist[(H - 1, W - 1, H - 2, W - 1)], dist[(H - 1, W - 1, H - 1, W - 2)])
print(ans) if ans != inf else print(-1)