题解 | 二维斐波那契数列

MOD = 10**9+7

n,m=map(int,input().split())

A = [[0]*m for _ in range(n)]

for i in range(n):
    A[i][0]=1
for j in range(m):
    A[0][j]=1

for i in range(1,n):
    for j in range(1,m):
        A[i][j]=(A[i-1][j]+A[i][j-1])%MOD

print(A[n-1][m-1])