题解 | #走方格的方案数#

def f(n,m):
    dp=[[0 for i in range(n+1)] for j in range(m+1)]
    if n<0 or m<0:
        return 0
    else:
        for j in range(m+1):
            dp[j][0] = 1
        for i in range(n+1):
            dp[0][i] = 1
        for j in range(1, m + 1):
            for i in range(1, n + 1):
                dp[j][i] = dp[j - 1][i] + dp[j][i - 1]
    return dp[m][n]
while True:
    try:
        n, m = map(int, input().split())
        print(f(n, m))
    except:
        break