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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sharif ullah:
20160420 14:32:20
O(N+logN) works! 

pamyjeela:
20160416 18:53:25
Thanks geek4geeks 

Santosh Kumar Shaw:
20160407 15:46:32
Done using only XOR operator. 

aboalmanal2000:
20160331 17:22:00
easy with sorting 

nonushikhar:
20160323 15:54:44
simple sort method accepted : 

syed_tanveer:
20160222 16:49:44
cout and cin gave a TLE . :/ 

abc_c:
20160207 08:14:18
Amazing!!


hamcom1212:
20160126 07:15:01
I used hash map in c++ but get TLE .. :( 

prateekmathur1991:
20160112 11:34:50
Got AC with Java... :) Needs fast I/O though... 

dokz:
20160106 10:25:01
The problem seems to be impossible in C# \ Java. 
Added by:  Efim 
Date:  20101104 
Time limit:  0.134s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 