Problem:
Score : 200 points

Problem Statement

There are N + 1 squares arranged in a row, numbered 0, 1, ..., N from left to right.

Initially, you are in Square X.
You can freely travel between adjacent squares. Your goal is to reach Square 0 or Square N.
However, for each i = 1, 2, ..., M, there is a toll gate in Square A_i, and traveling to Square A_i incurs a cost of 1.
It is guaranteed that there is no toll gate in Square 0, Square X and Square N.

Find the minimum cost incurred before reaching the goal.

Constraints

1 \leq N \leq 100

1 \leq M \leq 100

1 \leq X \leq N - 1

1 \leq A_1 < A_2 < ... < A_M \leq N

A_i \neq X

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N M X
A_1 A_2 ... A_M

Output

Print the minimum cost incurred before reaching the goal.

Sample Input 1

5 3 3
1 2 4

Sample Output 1

1

The optimal solution is as follows:

First, travel from Square 3 to Square 4. Here, there is a toll gate in Square 4, so the cost of 1 is incurred.

Then, travel from Square 4 to Square 5. This time, no cost is incurred.

Now, we are in Square 5 and we have reached the goal.

In this case, the total cost incurred is 1.

Sample Input 2

7 3 2
4 5 6

Sample Output 2

0

We may be able to reach the goal at no cost.

Sample Input 3

10 7 5
1 2 3 4 6 8 9

Sample Output 3

3

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io; // use宣言は関数内にも書けます
use std::str::FromStr;
use std::cmp;

  

macro_rules! get {
      ($t:ty) => {
          {
              let mut line: String = String::new();
              std::io::stdin().read_line(&mut line).unwrap();
              line.trim().parse::<$t>().unwrap()
          }
      };
      ($($t:ty),*) => {
          {
              let mut line: String = String::new();
              std::io::stdin().read_line(&mut line).unwrap();
              let mut iter = line.split_whitespace();
              (
                  $(iter.next().unwrap().parse::<$t>().unwrap(),)*
              )
          }
      };
      ($t:ty; $n:expr) => {
          (0..$n).map(|_|
              get!($t)
          ).collect::<Vec<_>>()
      };
      ($($t:ty),*; $n:expr) => {
          (0..$n).map(|_|
              get!($($t),*)
          ).collect::<Vec<_>>()
      };
      ($t:ty ;;) => {
          {
              let mut line: String = String::new();
              std::io::stdin().read_line(&mut line).unwrap();
              line.split_whitespace()
                  .map(|t| t.parse::<$t>().unwrap())
                  .collect::<Vec<_>>()
          }
      };
      ($t:ty ;; $n:expr) => {
          (0..$n).map(|_| get!($t ;;)).collect::<Vec<_>>()
      };
}

#[test]
fn test_1(){
   let expect = solve(5, 3, 3, vec![1, 2, 4]);   
   assert_eq!(1, expect);
}

#[test]
fn test_2(){
   let expect = solve(7, 3, 2, vec![4, 5, 6]);   
   assert_eq!(0, expect);
}

#[test]
fn test_3(){
   let expect = solve(10, 7, 5, vec![1, 2, 3, 4, 6, 8, 9]);   
   assert_eq!(3, expect);
}

fn solve(n: u32, m:u32, x:u32, mut ai:Vec<u32>) -> u32{
    ai.sort();
    let big     = ai.iter()
                    .enumerate()
                    .filter(|&(index, &digit)| digit > x)
                    .count();
    let small   = ai.iter()
                    .enumerate()
                    .filter(|&(index, &digit)| digit < x)
                    .count();

    cmp::min(big as u32, small as u32)
}

fn main() {

    let (n, m, x) = get!(u32, u32, u32);
    let mut ai = vec![1u32];
    
    let stdin = io::stdin();
    let mut buf = String::new();
    stdin.read_line(&mut buf).ok();

    let ai: Vec<u32> = buf.split_whitespace()
        .map(|n| u32::from_str(n).unwrap())
        .collect();

    let ans = solve(n, m, x, ai);

    println!("{}", ans);   
    
}