AE00  Rectangles
Byteman has a collection of N squares with side 1. How many different rectangles can he form using these squares?
Two rectangles are considered different if none of them can be rotated and moved to obtain the second one. During rectangle construction, Byteman can neither deform the squares nor put any squares upon any other ones.
Input
The first and only line of the standard input contains one integer N (1 <= N <= 10000).
Output
The first and only line of the standard output should contain a single integer equal to the number of different rectangles that Byteman can form using his squares.
Example
For the input data:
6
the correct result is:
8
Task author: Jakub Radoszewski.
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akash619j:
20170419 08:07:10
AC on one go though took about 3035 mins to be sure of correctness of my soln!!


nonushikhar:
20170330 20:31:43
AC in one go


xprilion:
20170321 09:40:15
AC in one! my 6th! :D 

ankitshrey112:
20170311 12:34:20
little bit of math...


sina_ss:
20170308 11:30:46
: badihie


tuandayhehe:
20170214 08:29:38
AC in 1 GO with 5 lines :"> 

dgfreak:
20170124 17:15:45
Using some elementary summing formulas, you can get it down to a formula that's calculated in O(sqrt(n)) time. 

vetox:
20170103 12:57:10
Calculating the number of possible rectangles for each squares takes O( sqrt(n) ) time. To do that for n numbers 1, 2, 3, 4.....n, takes O( n * sqrt(n) ) operations. So that makes it O(n ^ 1.5) complexity.


ignacio:
20161227 07:31:46
Nice problem 

shantanu_sarin:
20161206 23:17:12
Just try to judge the pattern .......for n=2,3,4.......15 and your job is done...

Added by:  Race with time 
Date:  20090503 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  Algorithmic Engagements 2009 