CSES - Grid Paths
  • Time limit: 1.00 s
  • Memory limit: 512 MB
Consider an $n \times n$ grid whose top-left square is $(1,1)$ and bottom-right square is $(n,n)$.

Your task is to move from the top-left square to the bottom-right square. On each step you may move one square right or down. In addition, there are $m$ traps in the grid. You cannot move to a square with a trap.

What is the total number of possible paths?


The first input line contains two integers $n$ and $m$: the size of the grid and the number of traps.

After this, there are $m$ lines describing the traps. Each such line contains two integers $y$ and $x$: the location of a trap.

You can assume that there are no traps in the top-left and bottom-right square.


Print the number of paths modulo $10^9+7$.

  • $1 \le n \le 10^6$
  • $1 \le m \le 1000$
  • $1 \le y,x \le n$

3 1
2 2