Jan2019SilverIII

import java.io.*;
import java.util.*;

public class mountain {

    public static void main(String[] args) throws java.io.IOException {
      BufferedReader in = new BufferedReader(new FileReader("mountains.in"));
      PrintWriter out = new PrintWriter(new FileWriter("mountains.out"));
      StringTokenizer tok = new StringTokenizer(in.readLine());

      int numMts = Integer.parseInt(tok.nextToken());
      ArrayList<Mt> mountains = new ArrayList<>();
      int peakX = 0;
      int peakY = 0;
      for (int i = 0; i < numMts; i++) {
        tok = new StringTokenizer(in.readLine());
        peakX = Integer.parseInt(tok.nextToken());
        peakY = Integer.parseInt(tok.nextToken());
        Mt newMount = new Mt(peakX, peakY);
        mountains.add(newMount);
      }

      int count = 0;
      for(Mt m1: mountains) {
        if (m1.visible == true) {
          for (Mt m2: mountains) {
            if (m2.visible == true){
              if (m1.compareTo(m2) == Mt.CONTAINS) {
                m2.visible = false;
              }
            }
          }
        }
      }

      for (int i = 0; i < mountains.size(); i++) {
        if (mountains.get(i).visible == true) {
          count++;
        }
      }

      out.println(count);
      out.close();
      in.close();

    }
}

class Mt implements Comparable<Mt> {
  public boolean visible = true;
  public static final int CONTAINS = 1;
  public static final int EQUALS = 0;
  public static final int DISTINCT = -1;
  public int int1;
  public int int2;

  public Mt(int x, int y) {
    this.int1 = y - x;
    this.int2 = x + y;
  }

  public int compareTo(Mt other) {
    if(this.int1 == other.int1 && this.int2 == other.int2) {
      return EQUALS;
    } else if (this.int1 >= other.int1 && this.int2 >= other.int2) {
      return CONTAINS;
    }
    return DISTINCT;
  }
}