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
Luis Herrera:
20160514 21:58:59
I used binary search but it looks that there is a simpler solution... 

lalit_nit:
20160209 04:51:17
Just by Given TestCases and Brute Force => :) Last edit: 20160209 04:51:57 

akshayvenkat:
20160112 09:25:57
pretty simple logic. (4*n1)/3 is perfect square , its a beehive number. thank you @ashish Last edit: 20160309 16:36:53 

ABHISHEK RAJPUT:
20151217 20:49:17
construct beehive structure by yourself first...see series,make formula and


rajesh1995:
20151125 04:38:52
easy...at every level 6*(n1) added to next level....brute approach....acptd


sumit suthar:
20151114 06:35:47
Take it eazy... :) 

alexbandeira:
20150922 21:01:28
one line: return rec(n,s+=(*****),i+1); (= Last edit: 20150922 21:02:04 

Abishek:
20150912 16:05:55
don't think hard ! brute force got accepted ! 

Shivam Singh:
20150824 11:03:30
Level 1  1


Ashish:
20150819 15:49:09
N is beehive iff (4N1)/3 is a perfect square. This problem is pretty shitty. Last edit: 20150819 17:14:05 
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 