find your present (2)

find your present (2)

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 16857    Accepted Submission(s): 6341

Problem Description

In the new year party, everybody will get a "special present".Now it's your turn to get your special present, a lot of presents now putting on the desk, and only one of them will be yours.Each present has a card number on it, and your present's card number will be the one that different from all the others, and you can assume that only one number appear odd times.For example, there are 5 present, and their card numbers are 1, 2, 3, 2, 1.so your present will be the one with the card number of 3, because 3 is the number that different from all the others.

 

Input

The input file will consist of several cases. 
Each case will be presented by an integer n (1<=n<1000000, and n is odd) at first. Following that, n positive integers will be given in a line, all integers will smaller than 2^31. These numbers indicate the card numbers of the presents.n = 0 ends the input.

 

Output

For each case, output an integer in a line, which is the card number of your present.

 

Sample Input

  

   5
1 1 3 2 2
3
1 2 1
0
  

 

Sample Output

  

   3
2


   

    

     Hint
    
Hint
   
    
use scanf to avoid Time Limit Exceeded
  

 

Author

8600

这一题用异或解决特别好使，估计作者也不想让你用数组存，因为n太大！首先将temp的值设为0，因为0与任何数的异或都等于任何数，任何数与其身异或还是0.其次当temp为某个单数时，temp与其他偶数次数异或之后值不变，这也是做题的关键之一

比如 2 2 3 1 1 

其二进制数分别对应为10 10 11 01 01

0与10异或结果为10， 10与10异或为0， 0与11异或为11，11与01异或为10 ，10与01异或为11,11的二进制是3

关于异或的详解，请见于异或详解