import sys
n,m=list(map(int,input().split()))
dp=[[1 for _ in range(m+1)] for _ in range(n+1)]

for i in range(1,n+1):
    for j in range(1,m+1):
        dp[i][j]=dp[i][j-1]+dp[i-1][j]
print(dp[n][m])

dp[i][j] = dp[i-1][j]+dp[i][j-1]

默认原始数据是1

就是表示下一个斜方的可能数是两个之和