Problem1170--综合练习---求和1

1170: 综合练习---求和1

Time Limit: 1 Sec  Memory Limit: 128 MB
Submit: 563  Solved: 399
[Status] [Submit] [Creator:]

Description

求1-2+3-4+5-6+7-8+...+n的和 

Input

输入一个正整数n， (n<=100)

Output

输出算式的结果

Sample Input Copy 

4

Sample Output Copy 

-2

Source/Category

 
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