A recurring meetup group keeps a signup roster. Every signup has a unique registration id (a positive integer, not necessarily assigned in order) and an email address, exactly as the attendee typed it (case matters — two emails that differ only in letter case count as different addresses). Because the same person sometimes fills out the form more than once, the organizers want to keep, for every email address that appears, only the signup with the smallest registration id, and purge every other signup sharing that same email address. Signups whose email address is unique in the roster are never purged.

Given the roster, determine exactly which registration ids must be purged.

Input format

• Line 1: an integer n — the number of signups on the roster.
• The next n lines: each gives one signup as two whitespace-separated tokens, id email, where id is the registration id and email is the signup's email address (a token with no whitespace).

Output format

• Line 1: an integer k — the number of registration ids to purge.
• Line 2: the k purged registration ids, in ascending order, separated by single spaces (this line may be empty when k is 0).

Constraints

• 1 <= n <= 20000
• 1 <= id <= 10^9, and all ids in the roster are distinct
• 1 <= length of each email <= 40, containing no whitespace characters
• Comparisons between email addresses are exact and case-sensitive

4
1 alice@example.com
2 alice@example.com
3 bob@example.com
4 alice@example.com

2
2 4

3
5 a@x.com
6 b@x.com
7 c@x.com

0