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1176.   Recaman's Sequence
Time Limit: 3.0 Seconds   Memory Limit: 65536K
Total Runs: 1885   Accepted Runs: 923



The Recaman's sequence is defined by a0 = 0 ; for m > 0, am = am-1 - m if the resulting 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: China 2004 - Shanghai Preliminary
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