Problems
Simple Question
Simple Question
Given integer n, you must calculate the sum of all integers between 1 and n (including 1 and n).
Input data
Each line has one integer n~(|n| \le 10000). The last line contains 0 and is not processed.
Output data
For each value of n print the answer on a separate line.
Examples
Input example #1
1 10 0
Output example #1
1 55