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**Task** | Statistics

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 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 $10^9+7$.

- $1 \le n \le 1000$

Input:

`4`

....

.*..

...*

*...

Output:

`3`