- Time limit: 1.00 s
- Memory limit: 512 MB
Your task is to calculate the number of paths from the upper-left square to the lower-right square where you only can 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 $10^9+7$.
- $1 \le n \le 1000$