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_BegginerContest94_Question2
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            int n = Int32.Parse(input[0]);
            int m = Int32.Parse(input[1]);
            int x = Int32.Parse(input[2]);

            string[] input2 = Console.ReadLine().Split(' ');

            int[] mass = new int[100];

            foreach (var i in input2)
            {
                mass[Int32.Parse(i)] = 1;
            }
            //x to n
            int costToN = 0;
            for (int i = x; i < n; i++)
            {
                if (mass[i] == 1) costToN++;
            }

            //x to 0
            int costToZero = 0;
            for (int i = x; i > 0; i--)
            {
                if (mass[i] == 1) costToZero++;
            }

            if (costToZero < costToN)
            {
                Console.WriteLine(costToZero);
            }
            else
            {
                Console.WriteLine(costToN);
            }
        }
    }
}