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::stdin;
use std::cmp::min;

fn main() {
    let mut buf = String::new();
    stdin().read_line(&mut buf).unwrap();
    let mut n_m_x: Vec<i32> = Vec::with_capacity(3);
    for iter in buf.split_whitespace(){
        n_m_x.push(iter.parse::<i32>().unwrap());
    }

    buf.clear();
    stdin().read_line(&mut buf).unwrap();
    let mut cost_array: Vec<i32> = Vec::new();
    for iter in buf.split_whitespace(){
        cost_array.push(iter.parse::<i32>().unwrap());
    }

    println!("{}", solve(n_m_x, cost_array));
}

fn solve(n_m_x: Vec<i32>, cost_array: Vec<i32>) -> i32 {
    let n = n_m_x[0];
    let x = n_m_x[2] as usize;

    let mut cost = vec![0; n as usize];
    for index in cost_array {
        cost[index as usize] = 1;
    }
    cost[x] = 0;

    let (left, right) = cost.split_at(x);
    min(left.iter().sum(), right.iter().sum())
}