Given an array A of N positive numbers and an integer P. Let NumPairs, be the number of pairs of elements of array A, such that their bitwise xor equal to X. You need to find the largest X, such that NumPairsx is greater or equal to P. If no such X exists print -1. Constraints:

N <=10 pow 4 P <=10 pow 9 Ai <=10 pow 9

Example:

A [1,12,13,14], P=1

QUESTION IS FROM PREVIOUS YEAR COMPANY QUESTIONS NOT FROM ANY ONGOING CONTEST