求解一道ACM习题,北大OJ2081

求解一道ACM习题,北大OJ2081
Description
The Recaman's sequence is defined by a0 = 0 ; for m > 0,am = am−1 − m if the rsulting am is positive and not already in the sequence,otherwise am = am−1 + m.
The first few numbers in the Recaman's Sequence is 0,1,3,6,2,7,13,20,12,21,11,22,10,23,9 ...
Given k,your task is to calculate ak.
Input
The input consists of several test cases.Each line of the input contains an integer k where 0