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 Go (1.14.1) (judge verdict: Wrong Answer)

package main
import (
	"fmt"
)

func notExist(l []int, i int) bool{
  flag := true
  for _, v := range l {
    if v == i {
      flag = false
      return flag
    }
  }
  return flag
}

func loop (x, n int, l []int) int {
  ans := x
  for i:=0; i < n; i++ {
    for j := -1; j != 3; j +=2{
      if notExist(l, x + i * j) {
        ans = x + i * j
        return ans
      }
    }
  }
  return ans
}

func main() {
  var x, n, a int
  fmt.Scan(&x)
  fmt.Scan(&n)
  l := make([]int, n)
  for i:=0; i < n; i++ {
    fmt.Scan(&a)
    l[i] = a
  }

  ans := loop(x, n, l)
  fmt.Printf("%d\n", ans) 
}