def read_data():
    W, H = map(int, input().split())
    M = [0] * (W + 3)
    for row in range(H):
        M.extend(list(map(int, input().split())))
        M.extend([0, 0])
    M.extend([0] * (W + 1))
    return W, H, M

def solve(W, H, M):
    H2 = H + 2
    W2 = W + 2
    H1 = H + 1
    W1 = W + 1
    goal = H1 * W2 - 2
    start = W2 + 1
    frontiers = []
    if M[start + 1] != M[start]: frontiers.append((start + 1, start))
    if M[start + W2] != M[start]: frontiers.append((start + W2, start))
    visited = set(frontiers)
    dist = 1
    while frontiers:
        dist += 1
        new_frontiers = []
        for pos1, pos2 in frontiers:
            val1 = M[pos1]
            val2 = M[pos2]
            dif = val1 - val2
            for new_pos in [pos1-1, pos1+1, pos1-W2, pos1+W2]:
                h, w = divmod(new_pos, W2)
                if w == 0 or h == 0 or w == W1 or h == H1 or new_pos == pos2: continue
                if (new_pos, pos1) in visited: continue
                new_val = M[new_pos]
                if new_val == val1 or new_val == val2: continue
                if dif * (new_val - val1) > 0: continue
                new_frontiers.append((new_pos, pos1))
                visited.add((new_pos, pos1))
                if new_pos == goal: return dist
        frontiers = new_frontiers
    return -1

W, H, M = read_data()
print(solve(W, H, M))