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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rakeshgupta:
20161217 13:37:45
Last edit: 20161218 08:27:15 

julkas:
20161217 10:22:58
Last edit: 20170305 15:32:46 

apurvgs:
20161214 06:48:33
cin and cout gives TLE


rakeshgupta:
20161213 11:33:09
@julkas what is "and ... 5 L. BR.??". Sorry, but i am a beginner in python, so not so well in acronyms (if it is one). Last edit: 20161213 11:37:24 

julkas:
20161206 09:24:29
One pass. O(N). 

asgupta_spoj:
20161203 20:14:53
easy question


julkas:
20161203 16:11:06


rakeshgupta:
20161201 17:42:27
Last edit: 20161213 11:37:49 

julkas:
20161130 22:15:57
Last edit: 20170305 15:33:54 

epsilonalpha:
20161127 00:36:55
Accepted in one go! Did a similar question back on HackerRank. 
Added by:  Efim 
Date:  20101104 
Time limit:  0.134s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 