import java.util.HashSet;
import java.util.Scanner;

public class Main {

	public static void main(String args[]) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int M = sc.nextInt();
		int X = sc.nextInt();
		HashSet<Integer> A = new HashSet<Integer>();
		for (int i = 0; i < M; i++)
			A.add(sc.nextInt());
		sc.close();

		int ansLeft = 0;
		int ansRight = 0;

		for (int i = X; i >= 0; i--)
			if (A.contains(i))
				ansLeft++;
		for (int i = X; i <= N; i++)
			if (A.contains(i))
				ansRight++;

		System.out.println(Math.min(ansLeft, ansRight));
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz