Tricky XOR

[hacker9876]

A project was going on related to image processing and to perform experiments and get desired result the image needs to be converted to Gray-Scale using a parameter 'x' and the function P(x) represented the Gray-Code and calculated via x xor (x div 2) where xor stands for bitwise exclusive OR (bitwise modulo 2 addition), and div means integer division.

It is interesting to note that function P(x) is invertible, which means it is always possible to uniquely restore x given the value of P(x).

So the group working on the project forgot to keep the original data related to parameter 'x'. Write a program to restore number x from the given value of P(x).

INPUT: The input file contains an integer number y, the value of G(x).

OUTPUT: The output file should contain a single integer x such that G(x) = y.

Sample Input: 15

Sample Output: 10

Can anyone clearly explain your solution's to this problem???

[Ganado]

Duplicate post of http://www.cplusplus.com/forum/beginner/245213/
Don't double-post.

[jonnin]

xor itself is reversible. Do you understand that much? This is just an extension of that property, really.