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: Accepted)

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(){
    int N = 0;
    int M = 0;
    int X = 0;
    int temp = 0;
    int cost = 0;
    int costA = 0;
    int costB = 0;
    int *map;
    int i;
    scanf("%d%d%d", &N, &M, &X);

    if ((1 > N) || (100 < N) || (1 > M) || (100 < M)){
        return 1;
    }
    if ((1 > X) || ((N - 1) < X)){
        return 1;
    }

    map = (int *)malloc(sizeof(int) * (N + 1));
    memset(map, 0, sizeof(map));

    for (i = 0; i < M; i++)
    {
        scanf("%d", &temp);
        if ((1 > temp) || ((N - 1) < temp) || (temp == X)){
            free(map);
            return 1;
        }
        map[temp] = 1;
    }

    for (i = X; i < N; i++){
        if (map[i] == 1){
            costA++;
        }
    }
    for (i = X; i > 0; i--){
        if (map[i] == 1){
            costB++;
        }
    }
    cost = (costA < costB) ? costA : costB;
    printf("%d\n", cost);

    free(map);
 
    return 0;
}