Problem 1118 Recaman＇s Sequence
Total Submit: 17
Time Limit: 1000ms
Memory Limit: 30720KB
The Recaman's sequence is defined by a(0)=0; for m>0, a(m)=a(m-1)-m if the resulting a(m) is positive and not already in the sequence, otherwise a(m)=a(m-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 a(k).
The input consists of several test cases. Each line of the input contains an integer k where 0<=k<=500000.
The last line contains an integer -1, which should not be processed.
For each k given in the input, print one line containing a(k) to the output.