- Time limit: 1.00 s
- Memory limit: 512 MB
Consider an n \times n grid whose squares may have traps. It is not allowed to move to a square with a trap.
Your task is to calculate the number of paths from the upper-left square to the lower-right square. You can only move right or down.
The first input line has an integer n: the size of the grid.
After this, there are n lines that describe the grid. Each line has n characters:
. denotes an empty cell, and
* denotes a trap.
Print the number of paths modulo 10^9+7.
- 1 \le n \le 1000
4 .... .*.. ...* *...