Score : 300 points
Given are an integer X and an integer sequence of length N: p_1, \ldots, p_N.
Among the integers not contained in the sequence p_1, \ldots, p_N (not necessarily positive), find the integer nearest to X, that is, find the integer whose absolute difference with X is the minimum. If there are multiple such integers, report the smallest such integer.
Input is given from Standard Input in the following format:
X N p_1 ... p_N
Print the answer.
6 5 4 7 10 6 5
8
Among the integers not contained in the sequence 4, 7, 10, 6, 5, the one nearest to 6 is 8.
10 5 4 7 10 6 5
9
Among the integers not contained in the sequence 4, 7, 10, 6, 5, the ones nearest to 10 are 9 and 11. We should print the smaller one, 9.
100 0
100
When N = 0, the second line in the input will be empty. Also, as seen here, X itself can be the answer.