Problem: You are given a set of n segments on the axis Ox, each segment has integer endpoints between 1 and m inclusive. Segments may intersect, overlap or even coincide with each other. Each segment is characterized by two integers l_i and r_i (1 ≤ l_i ≤ r_i ≤ m) — coordinates of the left and of the right endpoints. 

Consider all integer points between 1 and m inclusive. Your task is to print all such points that don't belong to any segment. The point x belongs to the segment [l; r] if and only if l ≤ x ≤ r.

Input

The first line of the input contains two integers n and m (1 ≤ n, m ≤ 100) — the number of segments and the upper bound for coordinates.

The next n lines contain two integers each l_i and r_i (1 ≤ l_i ≤ r_i ≤ m) — the endpoints of the i-th segment. Segments may intersect, overlap or even coincide with each other. Note, it is possible that l_i=r_i, i.e. a segment can degenerate to a point.

Output

In the first line print one integer k — the number of points that don't belong to any segment.

In the second line print exactly k integers in any order — the points that don't belong to any segment. All points you print should be distinct.

If there are no such points at all, print a single integer 0 in the first line and either leave the second line empty or do not print it at all.

Examples

Input

3 5
2 2
1 2
5 5


Output

2
3 4 


Input

1 7
1 7


Output

0

Note

In the first example the point 1 belongs to the second segment, the point 2 belongs to the first and the second segments and the point 5 belongs to the third segment. The points 3 and 4 do not belong to any segment.

In the second example all the points from 1 to 7 belong to the first segment.

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;
import java.util.StringTokenizer;


public class Main {

	static boolean visited[] ; 
	static boolean ends[] ;
	static long mod = 1000000007 ;
	static int lens[] ; 
	static int seeds[] ; 
	static char a[] ;
	static double total ; 
	public static ArrayList adj[] ; 
	public static long x,y ;
	public static ArrayList<Integer> xx ;	
	public static double dp[][][] ;
	public static void main(String[] args) throws IOException, InterruptedException {
		Scanner sc =  new Scanner(System.in) ;
		PrintWriter pw = new PrintWriter(System.out);

		int n = sc.nextInt() ;
		int m = sc.nextInt() ; 
		int arr[] = new int[m+1] ; 
		for (int i = 0; i < n; i++)
		{
			arr[sc.nextInt()-1]++; 
			arr[sc.nextInt()]--; 
		}

		int cum[] = new int[m+1]; 
		cum[0]=arr[0];
		for (int i = 1; i < cum.length; i++)
		{
			cum[i]=cum[i-1]+arr[i];
		}

		int ans=0 ;
		for (int i = 0; i < m; i++)
		{
			if(cum[i]==0)
				ans++;

		}
		System.out.println(ans);
		for (int i = 0; i < m; i++)
		{
			if(cum[i]==0)
				System.out.print((i+1)+" ");
		}

	}





	static boolean contains(int p[], int x)
	{

		for (int i = 0; i < p.length; i++)
		{
			if(x==p[i]) return true ;
		}
		return false; 
	}
	static void generate(int n)
	{
		if(n>=10000000)
			return ; 

		xx.add(n) ; 
		generate(Integer.parseInt("4"+n)) ;
		generate(Integer.parseInt("7"+n)) ;

	}


	static long pow(long base, int exp) {
		long res = 1;
		while(exp > 0) {
			if(exp % 2 == 1) {
				res = (res * base);
			}

			base = (base * base) ;
			exp /= 2;
		}

		return res;
	}
































	public static void dfss(int root , int len)
	{
		visited[root]=true ; 
		if(ends[root] && root!=0) lens[root] = len ; 

		for (int i = 0; i < adj[root].size(); i++)
		{
			int c= (int) adj[root].get(i) ; 
			if(visited[c]==false)
				dfss(c, len+1);
		}
	}

	public static void pr(int root ,  int seed){
		visited[root] = true ;
		int dv = adj[root].size()-1 ; 
		if(root==0) dv++ ;

		for (int i = 0; i < adj[root].size(); i++)
		{
			int c = (int)adj[root].get(i) ; 
			seeds[c]=dv*seed ;
		}

		for (int i = 0; i < adj[root].size() ; i++)
		{
			int c = (int)adj[root].get(i) ; 
			if(visited[c]==false)
				pr(c , seeds[c]);

		}

	}



	static class Scanner {
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}

		public String nextLine() throws IOException {
			return br.readLine();
		}

		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		public boolean ready() throws IOException {
			return br.ready();
		}

		public int[] nextIntArray(int n) throws IOException {
			int arr[] = new int[n];
			for (int i = 0; i <n ; i++)
			{
				arr[i] = Integer.parseInt(next());
			}
			return arr;
		}
		public long[] nextLongArray(int n) throws IOException {
			long arr[] = new long[n];
			for (int i = 0; i <n ; i++)
			{
				arr[i] = Long.valueOf(next());
			}
			return arr;
		}
	}


	public static long getGCD(long n1, long n2) {
		if (n2 == 0) {
			return n1;
		}
		return getGCD(n2, n1 % n2);
	}


	public static void shuffleA(ArrayList<Integer> ss){
		if(ss.size()==1)
			return ; 
		for (int i = 0; i < ss.size(); i++)
		{
			Random rand = new Random();

			int  n = rand.nextInt(ss.size()-1) + 0;

			int tmp = ss.get(n);
			ss.remove(n);
			ss.add(tmp);
		}
	}
	public static void shuffle(int[]x){
		if(x.length==1)
			return ; 
		for (int i = 0; i < x.length; i++)
		{
			Random rand = new Random();

			int  n = rand.nextInt(x.length-1) + 0;

			int tmp = x[n];
			x[n]=x[i] ;
			x[i]=tmp;
		}
	}
	public static int binaryy(int[] arr, int l, int r, int x)   /// begin by 0 and n-1
	{
		if (r>=l)
		{
			int mid = l + (r - l)/2;
			if (arr[mid]== x)
				return mid;
			if (arr[mid]> x)
				return binaryy(arr, l, mid-1, x);
			return binaryy(arr, mid+1, r, x);
		}
		return -1;
	}

	/// searching for the index of first elment greater than x
	public static int binary1(int[]arr , int x) {
		int low = 0, high = arr.length; // numElems is the size of the array i.e arr.size() 
		while (low != high) {
			int mid = (low + high) / 2; // Or a fancy way to avoid int overflow
			if (arr[mid] <= x) {
				/* This index, and everything below it, must not be the first element
				 * greater than what we're looking for because this element is no greater
				 * than the element.
				 */
				low = mid + 1;
			}
			else {
				/* This element is at least as large as the element, so anything after it can't
				 * be the first element that's at least as large.
				 */
				high = mid;
			}
		}
		return low ; // return high ; 
	}


	////// searching for last element less than X 
	//	public static int binary2(pair[]arr , int x) {
	//		int low = 0, high = arr.length; // numElems is the size of the array i.e arr.size() 
	//		while (low != high) {
	//			int mid = (low + high) / 2; // Or a fancy way to avoid int overflow
	//			if (arr[mid].x >= x) {
	//				/* This index, and everything below it, must not be the first element
	//				 * greater than what we're looking for because this element is no greater
	//				 * than the element.
	//				 */
	//				high=mid;
	//			}
	//			else {
	//				/* This element is at least as large as the element, so anything after it can't
	//				 * be the first element that's at least as large.
	//				 */
	//				low = mid+1 ; 
	//			}
	//		}
	//		return low ; // return high ; 
	//	}







	public static int binary(long []arr , long target , int low , long shift) {
		int high = arr.length; 
		while (low != high) {
			int mid = (low + high) / 2; 
			if (arr[mid]-shift <= target) {
				low = mid + 1;
			}
			else {
				high = mid;
			}
		}
		return low ; // return high ; 
	}
	public static boolean isLetter(char x){
		if(x+0 <=122 && x+0 >=97 )
			return true ;
		else if (x+0 <=90 && x+0 >=65 )
			return true ; 
		else return false; 
	}
	public static long getPrimes(long x ){
		if(x==2 || x==3 || x==1)
			return 2 ;
		if(isPrime(x))
			return 5 ;
		for (int i = 2; i*i<=x; i++)
		{
			if(x%i==0 && isPrime(i))
				return getPrimes(x/i) ;
		}
		return -1;
	}







	public static int lis( int[]a , int n){
		int lis[] = new int[n] ; 
		Arrays.fill(lis,1) ; 

		for(int i=1;i<n;i++)
			for(int j=0 ; j<i; j++)
				if (a[i]>a[j] &&  lis[i] < lis[j]+1)   
					lis[i] = lis[j] + 1;           

		int max = lis[0];

		for(int i=1; i<n ; i++)
			if (max < lis[i])
				max = lis[i] ;
		return (max);

		//			ArrayList<Integer> s = new ArrayList<Integer>() ;
		//			for (int i = n-1; i >=0; i--)
		//			{
		//				if(lis[i]==max)
		//				{
		//					s.add(a[i].z);
		//					max --; 
		//				}
		//			}
		//
		//			for (int i = s.size()-1 ; i>=0 ;  i--)
		//			{
		//				System.out.print(s.get(i)+" ");
		//			}
		//
	}
	public static int calcDepth(Vertix node){
		if(node.depth>0) return node.depth; 
		// meaning it has been updated before;
		if(node.parent != null)
			return 1+ calcDepth(node.parent);
		else
			return -1;
	}

	public static boolean isPrime (long num){
		if (num < 2) return false;
		if (num == 2) return true;
		if (num % 2 == 0) return false;
		for (int i = 3; i * i <= num; i += 2)
			if (num % i == 0) return false;
		return true;
	}


	public static ArrayList<Long> getDiv(Long n)
	{
		ArrayList<Long>  f = new ArrayList<Long>() ; 

		while (n%2==0)
		{
			if(!f.contains(2l))
			{f.add((long) 2) ;}
			n /= 2;
		}

		// n must be odd at this point.  So we can
		// skip one element (Note i = i +2)
		for (long i = 3; i <= Math.sqrt(n); i+= 2)
		{
			// While i divides n, print i and divide n
			while (n%i == 0)
			{
				if(!f.contains(i))f.add(i);
				n /= i;
			}
		}

		// This condition is to handle the case whien
		// n is a prime number greater than 2
		if (n > 2)
			if(!f.contains(n))f.add(n);


		return f ;



	}

	//		public static boolean dfs(Vertix v , int target){
	//			try{
	//				visited[v.i]= true ;
	//			} catch (NullPointerException e)
	//			{
	//				System.out.println(v.i);
	//			}
	//			if(v.i == target)
	//
	//				return true ;
	//			for (int i =0 ; i< v.neighbours.size() ; i++)
	//			{ 
	//
	//				Vertix child = v.neighbours.get(i) ;
	//				if(child.i == target){
	//					found = true  ; 
	//				}
	//				if(visited[child.i]==false){
	//					found |= dfs(child, target) ;
	//				}
	//			}
	//			return found; 
	//		}









	public static class Vertix{
		long i ; 
		int depth ;
		ArrayList<Vertix> neighbours ; 
		Vertix parent ; 
		Vertix child ; 


		public Vertix(long i){
			this.i = i ;
			this.neighbours = new ArrayList<Vertix> () ;
			this.parent = null ;
			depth =-1;
			this.child = null ;
		}
	}

	public static class pair implements Comparable<pair> {
		int x ; 
		int y ; 




		public pair(int x, int y ){

			this.x=x ; 
			this.y =y ;


		}


		@Override
		public int compareTo(pair p) {
			if(this.y-this.x > p.y-p.x)
				return 1 ; 
			else if (this.y-this.x == p.y-p.x) 
				return 0 ; 
			else 
				return -1 ;
		}




	}

	public static class pair2 implements Comparable<pair2>{
		int i ; 
		int j ;
		int plus ;

		public pair2(int i , int j , int plus){
			this.i =i ;
			this.j = j ; 
			this.plus = plus ;
		}

		@Override
		public int compareTo(pair2 p) {
			if(this.j > p.j)
				return 1 ; 
			else if (this.j == p.j) return 0 ;
			else 
				return -1 ;
		}


	}
	public static class point implements  Comparable<point>
	{
		int x, y ; 
		public point(int x,int y){
			this.x=x ; this.y=y;
		}
		@Override
		public boolean equals(Object o) {

			// If the object is compared with itself then return true  
			if (o == this) {
				return true;
			}

			/* Check if o is an instance of Complex or not
	          "null instanceof [type]" also returns false */
			if (!(o instanceof point)) {
				return false;
			}

			// typecast o to Complex so that we can compare data members 
			point c = (point) o;

			// Compare the data members and return accordingly 
			return Integer.compare(x, c.x) == 0
					&& Integer.compare(y, c.y) == 0;
		}
		@Override
		public int compareTo(point p) {
			if(this.x == p.x && this.y ==p.y)
				return 0 ; 
			else
				return -1 ; 
		}

		@Override
		public int hashCode()
		{
			return 15+x+(y%2) ;
		}



	}


}