Problem:
Score : 300 points

Problem Statement

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.

Constraints

1 \leq X \leq 100

0 \leq N \leq 100

1 \leq p_i \leq 100

p_1, \ldots, p_N are all distinct.

All values in input are integers.

Input

Input is given from Standard Input in the following format:

X N
p_1 ... p_N

Output

Print the answer.

Sample Input 1

6 5
4 7 10 6 5

Sample Output 1

8

Among the integers not contained in the sequence 4, 7, 10, 6, 5, the one nearest to 6 is 8.

Sample Input 2

10 5
4 7 10 6 5

Sample Output 2

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.

Sample Input 3

100 0

Sample Output 3

100

When N = 0, the second line in the input will be empty. Also, as seen here, X itself can be the answer.

Solution in C (GCC 9.2.1) (judge verdict: Accepted)

#include <stdio.h>

int X, N;
int p[128];

int main(void) {
	int i;
	if (scanf("%d%d", &X, &N) != 2) return 1;
	for (i = 0; i < N; i++) {
		if (scanf("%d" ,&p[i]) != 1) return 1;
	}
	for (i = 0; ; i++) {
		int t;
		for (t = X - i; t <= X + i; t += i == 0 ? 1 : i * 2) {
			int ok = 1;
			int j;
			for (j = 0; j < N; j++) {
				if (p[j] == t) ok = 0;
			}
			if (ok) {
				printf("%d\n", t);
				return 0;
			}
		}
	}
}