Samara 2018 C

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

public class C implements Runnable{
    public static void main (String[] args) {new Thread(null, new C(), "_cf", 1 << 28).start();}

    public void run() {
        FastScanner fs = new FastScanner();
        PrintWriter out = new PrintWriter(System.out);
        System.err.println("Go!");

        int n = fs.nextInt();
        Range[] a = new Range[2*n];
        for(int i = 0; i < n; i++) {
            int s = fs.nextInt(), e = fs.nextInt();
            a[i] = new Range(s, e, false);
            a[i + n] = new Range(s, e, true);
        }
        Arrays.sort(a);
        TreeSet<Integer> set = new TreeSet<>();
        for(Range r : a) {
            if(r.end == false) continue;
            Integer hi = set.ceiling(r.s);
            if(hi == null || hi > r.e) {
                set.add(r.e);
            }
        }

        out.println(set.size());
        while(!set.isEmpty()) {
            out.print(set.pollFirst());
            if(set.isEmpty()) out.println();
            else out.print(" ");
        }


        out.close();
    }

    class Range implements Comparable<Range> {
        int s, e, use;
        boolean end;
        Range (int a, int b, boolean f) {
            s = a; e = b;
            if(f) use = e;
            else use = s;
            end = f;
        }
        public int compareTo(Range o) {
            if(use == o.use) {
                return Boolean.compare(end, o.end);
            }
            return Integer.compare(use, o.use);
        }
    }

    void sort (int[] a) {
        int n = a.length;
        for(int i = 0; i < 50; i++) {
            Random r = new Random();
            int x = r.nextInt(n), y = r.nextInt(n);
            int temp = a[x];
            a[x] = a[y];
            a[y] = temp;
        }
        Arrays.sort(a);
    }

    class FastScanner {
        BufferedReader br;
        StringTokenizer st;
        public FastScanner() {
            try {
                br = new BufferedReader(new InputStreamReader(System.in));
                //                br = new BufferedReader(new FileReader("testdata.out"));
                st = new StringTokenizer("");
            } catch (Exception e){e.printStackTrace();}
        }
        public String next() {
            if (st.hasMoreTokens()) return st.nextToken();
            try {st = new StringTokenizer(br.readLine());}
            catch (Exception e) {e.printStackTrace();}
            return st.nextToken();
        }
        public int nextInt() {return Integer.parseInt(next());}
        public long nextLong() {return Long.parseLong(next());}
        public double nextDouble() {return Double.parseDouble(next());}

        public String nextLine() {
            String line = "";
            try {line = br.readLine();}
            catch (Exception e) {e.printStackTrace();}
            return line;
        }
        public Integer[] nextIntegerArray(int n) {
            Integer[] a = new Integer[n];
            for(int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }
        public int[] nextIntArray(int n) {
            int[] a = new int[n];
            for(int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }
        public char[] nextCharArray() {return nextLine().toCharArray();}
    }

}