NYOJ-sum of all integer numbers

NYOJ-sum of all integer numbers
Sum of all integer numbers time limit: 1000 MS | memory limit: 65535 KB difficulty: 0

Description

Your task is to find the sum of all integer numbers lying between 1 and NIntrusive.

Input

There are multiple test cases.
The input consists of a single integer N that is not greater than 10000 by it's absolute value.

Output

Write a single integer number that is the sum of all integer numbers lying between 1 and N random Sive.

Sample Input

3

Sample output

6

Code:

#include
     
      #include
      
       int main(){int n;while(~scanf("%d",&n)){if(n==0){printf("1\n");continue;}int k=1,t=0;  if(n<0)k=-1,t=1;n=abs(n);if(n&1)printf("%d\n",((n+1)>>1)*n*k+t);elseprintf("%d\n",(n>>1)*(n+1)*k+t);   }return 0;}