Description

Given a sequence b1, b2, b3… bn of odd length, the occurrence of every bi (i=1, 2, 3…n) is an even number except one number, the P number, which occurs odd times. Your task is to find that P number.

Input

The input file contains several test case, each test case starts with a line contains an odd number n (0<n<10 000), the length of the sequence, followed by a line with n numbers b1, b2, b3…bn. It is guaranteed that every bi (i=1, 2, 3..,n) can be represented by a signed integer. The input is terminated by a test case with n = 0. It should not be processed.

Output

For each test case, output a line the P number of the corresponding sequence.

Sample

Input

5
2 3 2 3 4
7
2 2 2 2 2 2 2
0

Output

4
2

Hint

O(n) algorithm exits.

Source: Limitfan