Python3 代码

def dfs (x, y):
    global a
    if x == n and y == m:
        a += 1
    else:
        if x < n:
            dfs (x + 1, y)
        if y < m:
            dfs (x, y + 1)

global n, m
a = 0
n, m = map(int, input().split())
a = 0

dfs (0, 0)
print (a)