CareerCup

A newly established university in New York has its campus located in a remote corner of the city. The university offers several courses and students are required to take a certain number of these courses. Each course publishes its schedule of lectures on a day-wise basis, i.e., it publishes the days of the week on which it holds lectures. Each course chooses exactly three days of the week for lectures. Travelling to the university is a nuisance and all the students who attend courses there, seek to minimise the number of days that they should have to travel. Given each course's schedule, you have to help the students decide on a combination of courses, such that they minimise the number of days that they have to travel to the university.
The university has strict attendance norms and it insists that students should attend all the lectures that their respective course offers.
Assume that the number of courses required will never be greater than the number of courses offered. In addition, there will be a unique combination of days, which allows the students to take the required number of courses and minimise travel.
Input specification:
First line will contain total number of courses (T) and the number of courses you are required to register (R) for.
The next T lines will each contain name of the course and those days on which the lectures for the course are held. The first word on each line is the name of the course and the rest of the words are three-letter words signifying the days of the week. E.g., "Physics MON WED FRI".
Output specification:
You should output the names of the days on which the student is required to go to the University to attend lectures. These should be printed on a single line in sorted order (SUN to SAT) with a single whitespace as a separator. Terminate the output with a newline.

Sample Input and Output:

Input:
6 3
Physics MON WED TUE
Chemistry TUE WED THU
Biology WED SAT THU
Economics MON FRI WED
English TUE WED FRI
History MON THU FRI

Output:
MON TUE WED FRI


Input:
6 2
Physics SUN TUE WED
Chemistry TUE WED THU
Biology THU WED FRI
Economics MON WED FRI
English THU TUE WED
History FRI MON THU

Output:
TUE WED THU