#3269. KPSUM - The Sum
KPSUM - The Sum
KPSUM - The Sum
题面翻译
题面
给你一个正整数 ,依次把 到 写下来,在每两个数字之间交替的加上加减号,求这个表达式的值。例如, 时,表达式为 。
。
题目描述
One of your friends wrote numbers 1, 2, 3, ..., N on the sheet of paper. After that he placed signs + and - between every pair of adjacent digits alternately. Now he wants to find the value of the expression he has made. Help him.
For example, if N=12 then +1 -2 +3 -4 +5 -6 +7 -8 +9 -1+0 -1+1 -1+2 = 5
输入格式
Each line contains one integer number N (1≤ N ≤ 10 ). Last line contains 0 and shouldn't be processed. Number of lines in the input does not exceed 40.
输出格式
For every line in the input write the answer on a separate line.
样例 #1
样例输入 #1
12
0
样例输出 #1
5