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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ianand:
20160527 16:26:46
Please


ragwave:
20160522 19:32:24
time limit is very strict so use scanf and printf! 

sahilagg06:
20160508 15:54:52
use scanf instead of cin. 

achi_9629:
20160504 14:53:01
good question learned something new 

rohittt:
20160430 21:50:45
requires a quite long line of code for java :( 

lalit_nit:
20160423 13:15:32
O(N+NlogN) gives TLE .... :( .. int is enough ...learnt something new 

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 
Added by:  Efim 
Date:  20101104 
Time limit:  0.134s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 