Group students by grade

Problem

A teacher has a list of students and the grade each one got. Group the names by grade.

Print one line per grade, in alphabetical order of grade, as grade: name1, name2. Sort the names inside each line alphabetically too.

Input: The first line is n. The next n lines each hold a student name and a grade separated by a space.
Output: One line per grade: the grade, a colon and a space, then the sorted names separated by a comma and a space.
Constraints: 1 ≤ n ≤ 1000
Names and grades have no spaces, and each name appears once

Example

Input

5
Ravi B
Asha A
Meena B
Kiran A
Dev C

Output

A: Asha, Kiran
B: Meena, Ravi
C: Dev

Three grades, two names in A and B.

Try the problem first. Open one hint at a time.

Hint 1

Use the grade as the key and a list of names as the value.

Hint 2

setdefault(grade, []) gives the list for a grade, creating it the first time. Sort the grades and then the names when printing.

Write your Python code, run it on the examples and submit it to hidden tests.