Number of schemes from the upper left corner to the lower right corner of the chessboard (2)

1. From the top left corner （1,1） To the lower right corner （n,m） The number of schemes is C（n + m - 2, n - 1）

2. The sum of the number of schemes from the upper left corner to the lower right corner is C（n + m - 1, n）- 1

3. The first n OK and yes C（n + m - 1, n）

Proof of the third point , You can see E Problem solving Codeforces Global Round 21 A-E - kilo The article - You know