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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function main(input) {
    var lines = input.split('\n');
    var line1 = lines[0].split(' ');
    var line2 = lines[1].split(' ');

    var N = parseInt(line1[0]);
    var M = parseInt(line1[1]);
    var X = parseInt(line1[2]);

    var tollgates = line2.map(function(str){return parseInt(str)});

    var costBeforeX = tollgates.reduce(function(cost, place){
        return place <= X ? cost + 1 : cost;
    }, 0);

    var costAfterX = M - costBeforeX;

    var answer = Math.min(costBeforeX, costAfterX);
    console.log(answer);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));