BOJ11000.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

public class BOJ11000 {
    public static void main(String[] args) throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;
        int N = Integer.parseInt(br.readLine());
        int[][] arr = new int[N][2];
        PriorityQueue<Integer> pq = new PriorityQueue<>();
        for(int i = 0; i < N; i++){
            st = new StringTokenizer(br.readLine());
            arr[i][0] = Integer.parseInt(st.nextToken());
            arr[i][1] = Integer.parseInt(st.nextToken());
        }

        Arrays.sort(arr, new Comparator<int[]>() {
            public int compare(int[] o1, int[] o2){
                if(o1[0] == o2[0]) return o1[1] - o2[1];
                return o1[0] - o2[0];
            }
        });

        pq.add(arr[0][1]);

        for(int i = 1; i < N; i++){
            if(pq.peek() <= arr[i][0]){
                pq.poll();
            }

            pq.add(arr[i][1]);
        }
        System.out.print(pq.size());
    }
}