SP8217 XMAX - XOR Maximization

Given a set of integers S = { a $ _{1} $ , a $ _{2} $ , a $ _{3} $ , ... a $ _{|S|} $ }, we define a function X on S as follows: X( S ) = a $ _{1} $ ^ a $ _{2} $ ^ a $ _{3} $ ^ ... ^ a $ _{|S|} $ . (^ stands for bitwise 'XOR' or 'exclusive or') Given a set of N integers, compute the maximum of the X-function over all the subsets of the given starting set.

The first line of input contains a single integer N, 1

To the first line of output print the solution.