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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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. 

sanyam19:
20180109 16:03:42
learnt a vry gud concept frm ths Q.... :) 

karthik1997:
20180105 15:51:16
Man , int and xor are enough ! O(1) space is enough ! 

amankumarjha:
20180101 11:27:01
Taught me to use xor and %llu 

bani_raheja:
20171229 16:07:26
what is the point of having such problems if you want people to use Fast I/O? :3 

sai__teja_01:
20171129 19:29:18
easy problem ,if ur facing TLE use scanf and printf instead cin and cout ,if ur using c++ 

hitesh87:
20171005 22:42:39
Learned to use xor.AC in many goes;p 

vishesh197:
20170923 17:22:15
just use xor as x^x=0 and x^0=x 

frobenius:
20170816 20:04:11
Unlike most other problems, do not put a newline at the end of your answer... it will count as wrong. 
Added by:  Efim 
Date:  20101104 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 