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

public class Main {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);

    int N = scanner.nextInt();
    int M = scanner.nextInt();
    int X = scanner.nextInt() - 1;
    Set<Integer> tolls = new HashSet<>();
    for (int i = 0; i < M; i++) tolls.add(scanner.nextInt() - 1);
    int left = 0, right = 0;
    for (int i = X; i >= 0; i--) if (tolls.contains(i)) left++;
    for (int i = X; i < N; i++) if (tolls.contains(i)) right++;
    System.out.println(Math.min(left, right));
  }
}

/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