[백준][Python] 1520번 내리막 길

import sys
sys.setrecursionlimit(10000)

m,n = map(int,input().split())
graph = []
for i in range(m):
    graph.append(list(map(int,input().split())))

visited = [[-1 for _ in range(n)] for __ in range(m)]

dx = [-1,1,0,0]
dy = [0,0,-1,1]

def dfs(x,y):
    
    if x == m - 1 and y == n - 1:
        return 1
    if visited[x][y] != -1:
        return visited[x][y]
    
    visited[x][y] = 0
    
    for i in range(len(dx)):
        
        nx = x + dx[i]
        ny = y + dy[i]
        
        if 0 <= nx < m and 0 <= ny < n:
            
            if graph[nx][ny] < graph[x][y] :
                
                visited[x][y] += dfs(nx,ny)
    
    return visited[x][y]

print(dfs(0,0))