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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anurag_tangri:
20170325 17:46:01
CAKEWALK :)


ameyanator:
20170320 06:23:42
Great problem to learn the xor gate!! :')


rohit9934:
20170307 17:04:41
MF semicolons give me 3 WA. Simple Use of XOR,Learnt XOR. 

nilabja16180:
20170215 19:01:29
AC in one GO! 

Fodor Gabor:
20170131 19:17:35
Python gets TLE, even for O(N) solution.


singhaljoy:
20170122 12:10:18
Use property of XOR, AC in 1 go!!! 

shantanu_sarin:
20170120 13:55:34
cin cout gives TLE


scorpion_ajay:
20170112 12:02:12
easiest till :p 

coder_with_a_h:
20170101 17:18:59
cin and cout gives TLE


vunnamtej:
20161229 18:11:31
@apurvgs thanks for your comment 
Added by:  Efim 
Date:  20101104 
Time limit:  0.134s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 