题解 | 走方格的方案数

def countsteps(n, m):

    if n<0 or m<0:
        return 0
    elif n==0 or m==0:
        return 1
    else:
        return countsteps(n, m-1) + countsteps(n-1, m)

def func():
    n, m = map(int, input().split())

    print(countsteps(n, m))


if __name__ == "__main__":
    func()