Description

Being unique is so important to people on Mars that even their lottery is designed in a unique way. The rule of winning is simple: one bets on a number chosen from [1, 10⁴]. The first one who bets on a unique number wins. For example, if there are 7 people betting on 5 31 5 88 67 88 17, then the second one who bets on 31 wins.

Input Format

Each input file contains one test case. Each case contains a line which begins with a positive integer N (<=10⁵) and then followed by N bets. The numbers are separated by a space.

Output Format

For each test case, print the winning number in a line. If there is no winner, print "None" instead.

7 5 31 5 88 67 88 17
5 888 666 666 888 888

31
None

Source

算法笔记 PAT 2012-08-25