Question: For a contest, you are searching for the top-m popular students of the university. You are given friends list of n students where some students may appear several times. Count the unique number of friends for each student and identify the top m popular students who have the most number of friends.

Input specification You will be given two integers in the beginning: the number of students (n) and top m students to list. In each of the following n lines, you will be given several positive integers (friends of the current student) ending with a negative number where 0 ≤ m ≤ n ≤ 8,000.

Output specification: Show the IDs (order of appearance) of top m students who have the most number of friends. If there are several students with the same number friends, first show the student with a smaller ID.

Explanation: Here is the list of students with their number of friends.
  1 -> 3
  2 -> 4
  3 -> 4
  4 -> 5
  5 -> 4
  6 -> 3
  7 -> 5