CRS - Crying Series


Monir is a student of class 8. He loves to learn new logic from Mathematics. Divergent Geometric Series is an interesting topic to him. So, He starts practicing to find the sum of the series in his everyday life. So he pick a standard series for Nth term,

F(x) = (-1)*1 + (-1)2* 2 + (-1)3* 3 + ..... + (-1) N*N

In this case, He asks for your help to find the value (algebraic sum) of F(x) from given series. As you are a great programmer in our country.

Input

Every line of the input contains a single integer N denoting the number of terms in the series.

Constraints

  • 0 ≤ N ≤ 1015

Output

For each test case, print a single line and the value (algebraic sum of all elements) of F(x) from given series.

Example

Input:
0
1
2
Output:
0
-1
1

hide comments
asad: 2018-07-02 14:36:30

thanks. @wisfaq

wisfaq: 2018-06-24 15:25:11

Be careful:
the sentence : The first line of the input contains a single integer N denoting the number of terms in the series is not correct.
every line of the input contains an N.
So process to eof.
Why have others with AC not mentioned this?

asad: 2018-06-24 14:09:38

ok

xynkt_99: 2018-06-24 13:24:17

should be moved to tutorial


Added by:asad_IT
Date:2018-06-24
Time limit:0.300s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All
Resource:Math