题解 | 二维斐波那契数列

n, m = map(int, input().split())
mod = 10 ** 9 + 7
p = 1 <= n, m <= 10 ** 3
a = [[0] * (m + 1) for _ in range(n + 1)]
a[1][1] = 1
if p:
    for i in range(2, n + 1):a[i][1] = a[i - 1][1]
    for j in range(2, m + 1):a[1][j] = a[1][j - 1]
    for i in range(2, n + 1):
        for j in range(2, m + 1):a[i][j] = a[i - 1][j] + a[i][j - 1]
    print(a[n][m] % mod)
else:print('请满足1≦n,m≦10^3的正整数')