import java.io.; import java.math.; import java.security.; import java.text.; import java.util.; import java.util.concurrent.; import java.util.regex.*;

public class Solution {

// Complete the queensAttack function below. static int queensAttack(int n, int k, int r, int c, int[][] obstacles) { HashMap> cache = new HashMap<>(); for (int i = 0; i < obstacles.length; i++) { if (cache.containsKey(obstacles[i][0])) { cache.get(obstacles[i][0]).add(obstacles[i][1]); } else { cache.put(obstacles[i][0], new HashSet()); cache.get(obstacles[i][0]).add(obstacles[i][1]); } } int counter = 0; // right for (int i = c + 1; i <= n; i++) { if (cache.containsKey(r) && cache.get(r).contains(i)) { break; } counter++; }

// left
for (int i = c - 1; i >= 1; i--) {
  if (cache.containsKey(r) && cache.get(r).contains(i)) {
    break;
  }
  counter++;
}

// down
for (int i = r + 1; i <= n; i++) {
  if (cache.containsKey(i) && cache.get(i).contains(c)) {
    break;
  }
  counter++;
}

// up
for (int i = r - 1; i >= 1; i--) {
  if (cache.containsKey(i) && cache.get(i).contains(c)) {
    break;
  }
  counter++;
}

// up-left
for (int i = r - 1, j = c - 1; i >= 1 && j >= 1; i--, j--) {
  if (cache.containsKey(i) && cache.get(i).contains(j)) {
    break;
  }
  counter++;
}

// up-right
for (int i = r - 1, j = c + 1; i >= 1 && j <= n; i--, j++) {
  if (cache.containsKey(i) && cache.get(i).contains(j)) {
    break;
  }
  counter++;
}

// down-right
for (int i = r + 1, j = c + 1; i <= n && j <= n; i++, j++) {
  if (cache.containsKey(i) && cache.get(i).contains(j)) {
    break;
  }
  counter++;
}

// down-left
for (int i = r + 1, j = c - 1; i <= n && j >= 1; i++, j--) {
  if (cache.containsKey(i) && cache.get(i).contains(j)) {
    break;
  }
  counter++;
}

return counter;

}

private static final Scanner scanner = new Scanner(System.in);

public static void main(String[] args) throws IOException { BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

String[] nk = scanner.nextLine().split(" ");

int n = Integer.parseInt(nk[0]);

int k = Integer.parseInt(nk[1]);

String[] r_qC_q = scanner.nextLine().split(" ");

int r_q = Integer.parseInt(r_qC_q[0]);

int c_q = Integer.parseInt(r_qC_q[1]);

int[][] obstacles = new int[k][2];

for (int i = 0; i < k; i++) {
  String[] obstaclesRowItems = scanner.nextLine().split(" ");
  scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");

  for (int j = 0; j < 2; j++) {
    int obstaclesItem = Integer.parseInt(obstaclesRowItems[j]);
    obstacles[i][j] = obstaclesItem;
  }
}

int result = queensAttack(n, k, r_q, c_q, obstacles);

bufferedWriter.write(String.valueOf(result));
bufferedWriter.newLine();

bufferedWriter.close();

scanner.close();

} }