Welcome to ZOJ
Information
Select Problem
Runs
Ranklist
ZOJ Problem Set - 2421
Recaman's Sequence

Time Limit: 2 Seconds      Memory Limit: 65536 KB

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 <= k <= 500000. The last line contains an integer -1, which should not be processed.


Output

For each k given in the input, print one line containing ak to the output.


Sample Input

7
10000
-1


Sample Output

20
18658


Source: Asia 2004, Shanghai (Mainland China), Preliminary
Submit    Status