题解 | 二维斐波那契数列

n,m = map(int,input().split())
dp  = [[0]*(m+1) for _ in range(n+1)]
dp[1][1] = 1
mod = 10**9+7
for i in range(2,n+1):
    dp[i][1] = dp[i-1][1] % mod
for j in range(2,m+1):
    dp[1][j] = dp[1][j-1] % mod
for i in range(2,n+1):
    for j in range(2,m+1):
        dp[i][j] = (dp[i][j-1] + dp[i-1][j]) % mod
print(dp[n][m])