OLOLO  Onotole needs your help
Onotole has a lot of pyani. Each pyani has a number, writing on it. Pyanis with equal numbers are indistinguishable. Onotole knows everything, so, he knows that each pyani appeared twice, and only one pyani is unique. He wants to get вздръжни эффект, and he needs the unique pyani. Given the list of pyanis denote which one of them appeared once (it is guaranteed that other pyanis appeared twice). 
Input
First line of input contains number of pyanis N <= 500 000. Next N lines contain a single positive integer 1 <= Pi <= 10^9.
Output
Output one positive integer on pyani, which appeared once.
Example
Input:
3
1
8
1
Output: 8
Onotole has found not optimal AC algorithms, so all solutions will be rejudged. He is watching you.
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pavanjupalli:
20180823 16:11:38
easy problem


puneetgargmnc:
20180812 16:30:09
Just use Fast I/O n u will get AC 

anupamshah:
20180704 13:29:43
A very nice problem .!


masterchef2209:
20180703 21:13:45
never realised XOR has such a cool use, good one 

theabd123:
20180530 16:14:41
THE POWER OF XOR 

incomplet_:
20180418 07:47:36
Don't using cin, cout, even with optimal algorithm this result in TLE 

pratikshit:
20180318 15:31:43
first time used XOR in a problem 

zephyr_96:
20180301 12:28:47
Better add JAVA to your list of unsupported languages. 

ayusofayush:
20180224 11:10:15
this problem teaches you the use of xor(^) operator 

abhijeetgurle:
20180210 05:59:24
Even if you write O(nlogn) solution it will get accepted using fast I/O. 
Added by:  Efim 
Date:  20101104 
Time limit:  0.134s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 