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:
nm = input().split(' ')
n =  int(nm[0])
m = int(nm[1])

starts = []
ends = []

coords = {}

for i in range(n):
	k = input().split(' ')
	starts.append(int(k[0]))
	ends.append(int(k[1]))

for p in starts:
	if coords.get(p) is None:
		coords[p]=1
	else:
		coords[p]=coords[p]+1

for p in ends:
	if coords.get(p) is None:
		coords[p]=-1
	else:
		coords[p]=coords[p]-1

#print(coords)

lines=0
ans=[]

for i in range(1,m+1):
	if coords.get(i) is not None:
		if coords[i]>0:
			lines+=coords[i]
		elif coords[i]==0:
			lines+=1

	if lines==0:
		ans.append(i)

	if coords.get(i) is not None:
		if coords[i]<0:
			lines+=coords[i]
		elif coords[i]==0:
			lines-=1

print(len(ans))
if len(ans)>0:
	for p in ans:
		print(p,end=" ")