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 PYTHON3):

Solution:
from __future__ import print_function
import sys
import math
import os.path
from copy import deepcopy
from functools import reduce


from collections import Counter, ChainMap, defaultdict
from itertools import cycle, chain
from queue import Queue, PriorityQueue
from heapq import heappush, heappop, heappushpop, heapify, heapreplace, nlargest, nsmallest
import bisect

from statistics import mean, mode, median, median_low, median_high


# CONFIG
sys.setrecursionlimit(10**9)

# LOG 
def log(*args, **kwargs):
    print(*args, file=sys.stderr, **kwargs)


# INPUT
def ni():
    return map(int, input().split())


def nio(offset):
    return map(lambda x: int(x) + offset, input().split())


def nia():
    return list(map(int, input().split()))


# CONVERT
def toString(aList, sep=" "):
    return sep.join(str(x) for x in aList)


def toMapInvertIndex(aList):
    return {k: v for v, k in enumerate(aList)}


# SORT
def sortId(arr):
    return sorted(range(len(arr)), key=lambda k: arr[k])


# MAIN

n,m = ni()

s = set(range(1,m+1))
for i in range(n):
    l,r = ni()
    ss = set(range(l, r+1))
    s -= ss

print(len(s))
print(toString(s))