364 - Sum of the Sequence

Sum of the Sequence

Time Limit: 1 sec

**The Problem**

Given an interesting sequence in below. In this problem you have to find out the result of the sequence.

**1 – 2 + 3 – 4 + 5 – 6 + 7 - . . . . . . . . . . . . . ***n* =??

*n*=??

** **

**Example:**

If n = 6 then

1 – 2 + 3 – 4 + 5 – 6 = -3

So the answer of this sequence is -3.

**The Input**

There are several lines of input. Each line contains a single integer **n (1<= n <=5000000)**. Input is terminated by **EOF**.

**The Output**

For each line, output the line “Case T: R” (Quotes for clarification), where T denote the test case and R denotes the result of the sequence.

**Sample Input**

6

10

**Sample Output**

Case 1: -3

Case 2: -5

Problem Setter: Milton Deb