Vardhaman college of engg. is conducting a coding challenge. The registrations are opened. Many people from different colleges are being registered for this event. Some of them are trying to make some errors in the registrations. They have registered there names more than one time by creating different e-mail ids. This became a real mess as the no. of registrations are very huge. To find out how many people have done this and who all done this. So, this problem is stated to the head of the registrations. He wanted you to help him to find out how many and who made this so that they can be eliminated. Help him to find a solution for this serious problem.

INPUT:
first line contains a number n which indicates no of applicants
next n lines will have the names

OUTPUT:
print  number which indicates no of illegal applicants
next lines print one name per line

NOTE: A applicant is considered illegal if it is repeated more than one

CONSTRAINTS:
0<n<100

0<name<20

SAMPLE INPUT
10
raghav
sitish
raghu
vishwa
kumar 
raghu
raghu
raghav
ritesh
deepesh

SAMPLE OUTPUT
2
raghav
raghu
'''
# Read input from stdin and provide input before running code

name = raw_input('What is your name?\n')
print 'Hi, %s.' % name
'''
n = input()
st = set([])
ans = set([])
for i in range(n):
	s = raw_input().lower()
	if s in st:
		ans.add(s)
	st.add(s)
print len(ans)
a = list(ans)
a.sort()
for x in a:
	print x