ROBOTGRI  Robots on a grid
You have recently made a grid traversing robot that can
nd its way from the top left corner of a grid to the
bottom right corner. However, you had forgotten all your
AI programming skills, so you only programmed your robot
to go rightwards and downwards (that's after all where the
goal is). You have placed your robot on a grid with some
obstacles, and you sit and observe. However, after a while
you get tired of observing it getting stuck, and ask yourself
\How many paths are there from the start position to the
goal position?", and \If there are none, could the robot have
made it to the goal if it could walk upwards and leftwards?"
So you decide to write a program that, given a grid of
size n x n with some obstacles marked on it where the robot
cannot walk, counts the dierent ways the robot could go
from the top left corner s to the bottom right t, and if none,
tests if it were possible if it could walk up and left as well.
However, your program does not handle very large numbers, so the answer should be
given modulo 2^31  1.
Input
On the rst line is one integer, 1 < n <= 1000. Then follows n lines, each with n characters,
where each character is one of '.' and '#', where '.' is to be interpreted as a walkable
tile and '#' as a nonwalkable tile. There will never be a wall at s, and there will never
be a wall at t.
Output
Output one line with the number of dierent paths starting in s and ending in t (modulo
2^31  1) or THE GAME IS A LIE if you cannot go from s to t going only rightwards and
downwards but you can if you are allowed to go left and up as well, or INCONCEIVABLE if
there simply is no path from s to t.
Example
Input: 5
.....
#..#.
#..#.
...#.
..... Output: 6
hide comments
Aditya Gourav:
20130325 21:19:13
wa in 21st test case


Rocker3011:
20121121 21:13:54
how does this modulo thing works? i need to do modulo each time i do something on my code? because i get tons of WA and i think it is because of that __


ɥsǝןǝǝu:
20121015 15:31:19
finally TLE.... 

TLE:
20120925 05:44:57
what about 18th test case,i m getting WA in 18th case... 

♘Prabhat:
20120827 18:41:10
finally AC..... 

Aradhya:
20120826 10:54:15
finally AC :) and ultimate problem if u want to learn bfs :D 

LeppyR64:
20120129 06:20:30
The answer for the sample input is definitely 6. 

Nishant:
20111231 13:46:49
can anyone plz explain the example ... there are 32 different ways of reaching from s to t in the given example ....


LeppyR64:
20111029 17:17:21
Two classic problems in one. Very nice, simple problem. 
Added by:  Krzysztof Lewko 
Date:  20111005 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 
Resource:  Nordic programming contest 