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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;

namespace AtCoder.ABC094
{
    class b
    {
        static void Main(string[] args)
        {
            var line = Console.ReadLine().Trim();
            var spl = line.Split(' ');
            var N = int.Parse(spl[0]);
            var M = int.Parse(spl[1]);
            var X = int.Parse(spl[2]);
            line = Console.ReadLine().Trim();
            spl = line.Split(' ');
            var list = new int[M];
            for(var i = 0; i < M; ++i)
            {
                list[i] = int.Parse(spl[i]);
            }
            for(var i = 0; i < M-1; ++i)
            {
                if (list[i] < X && list[i + 1] > X)
                {
                    Console.WriteLine(i + 1 > M - i - 1 ? M - i - 1 : i + 1);
                    return;
                }
            }
            Console.WriteLine(0);
        }
    }
}