Maths Challenge XOR4 .Can you please explain me this in detail

#1

Mike has got an array A of n numbers where binary representations of two consecutive numbers differ by only one bit. Now, he has a problem for you. He wants you to tell if there exists four numbers A[i1],A[ i2], A[i3],A[ i4] such that xor of these numbers is equal to 0. You can find this problem here.
Input Format

First line contains one integer n. Second line contains n space separated non-negative integers denoting the sequence A.

#2

@shellcodingblock
Here the array elements will be something like :- 1010 , 1000, 1001, 1101
as you can see the any adjacent numbers will have only 1 bit different from each other.
So, suppose if you take xor of first 2 in above, it is 0010.
Now let consider this, youf target is to find the other two numbers that it their xor is same to above value.

So, you just have to find four existing numbers in the such that their xor is 0.