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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DeviSree:
20150926 18:03:58
same sol TLE in python anyway nice question 

Sarthak Munshi:
20150920 13:17:29
ridiculous problem statement ! 

arabh_20:
20150919 09:13:49
xor method is easier ....way...


MSK:
20150918 04:26:54
did it in java tle :(


Mohit:
20150916 05:39:29
this question is really taught new thing.. 

:
20150911 15:28:53
50th problem :D 

Prakhar Dev Gupta:
20150911 11:01:05
1 1 2 3 4 will fetch what output and y? 

Abishek:
20150909 13:45:20
fast i/o needed . cost me two TLEs .. 

sneh sajal:
20150830 16:50:47
use scanf and think mathematically :) 

jack_jay:
20150825 13:44:19
easy.......taught me use of XOR.....and no use of long long in c++ 5.1.// 
Added by:  Efim 
Date:  20101104 
Time limit:  0.134s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 