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

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.

7 10000 -1

20 18658

Shanghai 2004 Preliminary