h, w = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(h)]
dp = [[0] * w for _ in range(h)]
lst = []
for i in range(h):
    for j in range(w):
        x = A[i][j] * h * w + i * w + j
        lst.append(x)

directions = [(-1, 0), (1, 0), (0, -1), (0, 1)]
lst.sort()
for tmp in lst:
    tmp %= h * w
    i = tmp // w
    j = tmp - i * w

    for di, dj in directions:
        ni, nj = i + di, j + dj
        if 0 <= ni < h and 0 <= nj < w and A[i][j] < A[ni][nj]:
            dp[ni][nj] = max(dp[ni][nj], dp[i][j] + 1)

ans = 0
for i in range(h):
    for j in range(w):
        ans = max(ans, dp[i][j])

print(ans + 1)