H, W = map(int, input().split())
A = []
D = []
for i in range(H):
    A.append(list(map(int, input().split())))
    for j in range(W):
        D.append((A[i][j], i, j))
        
D.sort()
B = [[1] * W for _ in range(H)]
dx = [1, 0, -1, 0]
dy = [0, 1, 0, -1]
for a, px, py in D:
    for k in range(4):
        x = px + dx[k]
        y = py + dy[k]
        if x < 0 or x > H - 1 or y < 0 or y > W - 1:
            continue
        if A[x][y] >= a:
            continue
        B[px][py] = max(B[px][py], B[x][y] + 1)
        
print(max([max(B[i]) for i in range(H)]))