from functools import lru_cache
from itertools import product, chain

import numpy as np

arr = np.array([[8,4,1],[6,5,2]])

def solve(arr_input):
    w, h = arr_input.shape
    @lru_cache
    def gen_dept(x, y):
        return max(chain((
            gen_dept(new_x, new_y)
            for value, (new_x, new_y) in filter(
            lambda c: c[0]<arr_input[x, y],
            ((arr_input[coords], coords)
             for coords in filter(
                lambda c: w>c[0]>=0 and h>c[1]>=0,
                ((x-1, y), (x+1, y), (x, y+1), (x, y-1))
            )))), (0, ))) + 1
    print(max(gen_dept(i,j) for i, j in product(range(w), range(h))))


if __name__ == '__main__':
    solve(arr)
    pass