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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os"

	"strconv"
)

func solve(in io.Reader, out io.Writer) error {
	sc := bufio.NewScanner(in)
	sc.Split(bufio.ScanWords)
	_, m, x := nextInt(sc), nextInt(sc), nextInt(sc)

	a := make([]int, m)
	lc, rc := 0, 0
	for i := 0; i < m; i++ {
		a[i] = nextInt(sc)

		if a[i] < x {
			lc++
		} else {
			rc++
		}
	}

	if lc < rc {
		fmt.Fprintln(out, lc)
	} else {
		fmt.Fprintln(out, rc)
	}

	return nil
}

func nextInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return i
}

func main() {
	err := solve(os.Stdin, os.Stdout)
	if err != nil {
		log.Fatal(err)
	}
}