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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
int main(void){
    // N+1マス左右　0,1.....N
    //自分の位置X
    //0またはNでゴール
    
    
    int N,M,X;
    scanf("%d %d %d",&N,&M,&X);
    int Ai[M];
    int costN = 0;
    int cost0 = 0;
    for(int i = 0;i<M;i++){
        scanf("%d",&Ai[i]);
        if(Ai[i]<X){
            //0へ向かう時のコスと
            cost0++;
        }else{
            costN++;
        }
        
    }
    int x_n = N-X;
    // int x_0 = X
    
    int n_0Flg = 0; // 0へ向かう
    if(X > x_n){
        n_0Flg = 1; // nヘ向かう
    }
    if(X == x_n && costN<cost0){
        n_0Flg = 1; //nへ向かう（コスト比）
    }
    int result = 0;
    if(n_0Flg == 0){
        printf("%d",cost0);
    }else{
        printf("%d",costN);
    }
    return 0;
    
}