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:
#      
import collections, atexit, math, sys
from functools import cmp_to_key
#key=cmp_to_key(lambda x,y: 1 if x not in y else -1 )

sys.setrecursionlimit(1000000)
def getIntList():
    return list(map(int, input().split()))    

import bisect 
try :
    #raise ModuleNotFoundError
    import numpy
    def dprint(*args, **kwargs):
        print(*args, **kwargs, file=sys.stderr)
    dprint('debug mode')
except ModuleNotFoundError:
    def dprint(*args, **kwargs):
        pass


def memo(func):  
    cache={}  
    def wrap(*args):  
        if args not in cache:  
            cache[args]=func(*args)  
        return cache[args]  
    return wrap

@memo
def comb (n,k):
    if k==0: return 1
    if n==k: return 1
    return comb(n-1,k-1) + comb(n-1,k)

inId = 0
outId = 0
if inId>0:
    dprint('use input', inId)
    sys.stdin = open('input'+ str(inId) + '.txt', 'r') #标准输出重定向至文件
if outId>0:
    dprint('use output', outId)
    sys.stdout = open('stdout'+ str(outId) + '.txt', 'w') #标准输出重定向至文件
    atexit.register(lambda :sys.stdout.close())     #idle 中不会执行 atexit
    
N, M= getIntList()
zz = set()
for i in range(N):
    l,r = getIntList()
    for j in range(l,r+1):
        zz.add(j)
print(M-len(zz))
for i in range(1,M+1):
    if i not in zz:
        print(i,end = ' ')