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)

//https://qiita.com/tanakh/
#[allow(unused_macros)]
macro_rules! input {
	(source = $s:expr, $($r:tt)*) => {
		let mut iter = $s.split_whitespace();
		let mut next = || { iter.next().unwrap() }; 
		input_inner!{next, $($r)*}
	};
	($($r:tt)*) => {

		let stdin = std::io::stdin();
		let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); 
		let mut next = move || -> String{
			bytes
				.by_ref()
				.map(|r|r.unwrap() as char) 
				.skip_while(|c|c.is_whitespace()) 
				.take_while(|c|!c.is_whitespace()) 
				.collect()
			};
	input_inner!{next, $($r)*} 
	};
}

#[allow(unused_macros)]
macro_rules! input_inner { 
	($next:expr) => {}; 
	($next:expr, ) => {};

	($next:expr, $var:ident : $t:tt $($r:tt)*) => { 
		let $var = read_value!($next, $t); 
		input_inner!{$next $($r)*}
	}; 
}
#[allow(unused_macros)]
macro_rules! read_value { 
	($next:expr, ( $($t:tt),* )) => {
		( $(read_value!($next, $t)),* ) 
	};
	
	($next:expr, [ $t:tt ; $len:expr ]) => {
		(0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
	};

	($next:expr, chars) => {
		read_value!($next, String).chars().collect::<Vec<char>>()
	};
	
	($next:expr, bytes) => {
		read_value!($next, String).into_bytes()
	};
	
	($next:expr, usize1) => { 
		read_value!($next, usize) - 1
	};

	($next:expr, $t:ty) => {
		$next().parse::<$t>().expect("Parse error")
	};
}

fn main(){
    input!{
        n : i64,
        m : usize,
        x : i64,
        a : [i64; m],
    }
    let mut count1 : i64 = 0;
    let mut count2 : i64 = 0;
    for i in 0..m {
        if a[i] < x {
            count1 = count1 + 1;
        } else {
            count2 = count2 + 1;
        }
    }
    if count1 < count2 {
        println!("{}",count1);
    } else {
        println!("{}",count2);
    }
}