import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class Main {

	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] tmp = br.readLine().split(" ");
		int N = Integer.parseInt(tmp[0]);
		int M = Integer.parseInt(tmp[1]);
		int X = Integer.parseInt(tmp[2]);
		List<Integer> A = new ArrayList<Integer>();
		tmp = br.readLine().split(" ");
		for(int i = 0;i<M;i++){
			A.add(Integer.parseInt(tmp[i]));
		}
		int countL = 0;
		int countR = 0;
		//左へ行く場合
		for(int l = X;l>0;l--){
			if(A.contains(l))countL++;
		}
		//右へいく場合
		for(int r = X;r<=N;r++){
			if(A.contains(r))countR++;
		}

		System.out.println(Math.min(countL,countR));
	}


}

/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