BEENUMS  Beehive Numbers
A beehive is an enclosed structure in which some honey bee species live and raise their
young. In this problem we consider a twodimensional sketch of the beehives. Each
beehive is composed of a certain number of cells, where each cell is a regular hexagon.
Each cell may have some neighbors, which are other cells that share a side with that cell.
A cell with exactly 6 neighbors is an internal cell, while a cell with fewer neighbors is an
external one. Notice that an external cell can always be changed to internal by adding
some neighbor cells.
We are interested in a particular class of beehives. This class of valid beehives is defined
recursively as follows: a) a single cell is a valid beehive; and b) given a valid beehive B,
if we add the minimum number of cells such that each external cell of B becomes an
internal cell, the result is a valid beehive.
The number of cells in a valid beehive is called a beehive number. Given an integer N ,
you must decide whether it is a beehive number.
Input
Each test case is described using a single line. The line contains an integer N (1 ≤ N ≤
10^{9} ). The end of input is indicated with a line containing a single −1.
Output
For each test case, output a single line containing an uppercase “Y” if N is a beehive
number, or an uppercase “N” otherwise.
Example
Input:
43
1
7
19
15
1
Output:
N
Y
Y
Y
N
hide comments
spartax:
20161206 22:30:34
See the sequence 1, 1 + 6, 1 + 6 + 12, ... and you will get the solution 

Simran Saha:
20161118 08:03:47
I am having difficulty in understanding the problem. Can anybody give a better explanation? 

epsilonalpha:
20161103 02:38:34
48th :)


narutohokage_1:
20161023 08:55:29
Do not see comments for hint . Because you can always find a better method , find your own method (Some methods in comment are more time efficient than others so you must try it yourself and then optimize it if it fails) , question is easy . Do not give up and draw diagram for more understanding. Also dont forget it Y and N not Yes and No. 

angel_of_death:
20161021 19:32:12
Was printing something out to debug the code and forgot to comment it out before submitting. Resulted in multiple WA. FML! 

sayedathar11:
20160818 15:27:59
Very Easy problem if You can observe pattern and apply brute force :) ;) 

ghost_wire:
20160729 08:38:53
comment helps a lot but it also destroy the pleasure of problem so please don't post the logic only post hint to that. 

sssymm:
20160727 05:08:42
@vector1996 touche 

vector1996:
20160715 20:01:43
long  WA


SANDEEP KUMAR:
20160712 11:38:56
Solved each query in O(1) with a bit precomputation... 
Added by:  Pablo Ariel Heiber 
Date:  20100926 
Time limit:  0.666s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: NODEJS objc VB.net 
Resource:  FCEyN UBA ICPC Selection 2010 