[백준] 1931번 회의실 배정

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

class Time implements Comparable<Time>{
	public int start, end;
	
	Time(int start, int end){
		this.start = start;
		this.end = end;
	}
	
	@Override
	public int compareTo(Time o) {
	    if (this.end == o.end) {
	        return this.start - o.start;
	    } else {
	        return this.end - o.end;
	    }
	}
}

public class Main {
	public static void main(String[] args) {
		
		Scanner kb = new Scanner(System.in);
		int N = kb.nextInt();
		List<Time> list = new ArrayList<>();
		
		for(int i=0; i<N; i++) {
			int s = kb.nextInt();
			int e = kb.nextInt();
			list.add(new Time(s, e));
		}
		
		int count = 0;
		int endTime = 0;
		
		Collections.sort(list);
		
		for(Time x: list) {
			if(x.start>= endTime) {
				count++;
				endTime = x.end;
			}
		}
		System.out.println(count);

	}

}