## Problem A: The Trip, 2007

A number of students are members of a club that travels annually to exotic locations. Their destinations in the past have included Indianapolis, Phoenix, Nashville, Philadelphia, San Jose,
Atlanta, Eindhoven, Orlando, Vancouver, Honolulu, Beverly Hills, Prague, Shanghai,
and San Antonio. This spring they are hoping to make a similar trip but aren't
quite sure where or when.
An issue with the trip is that their very generous sponsors always give them various
knapsacks and other carrying bags that they must pack for their trip home. As the airline
allows only so many pieces of luggage, they decide to pool their gifts and to pack
one bag within another so as to minimize the total number of pieces they must carry.

The bags are all exactly the same shape and differ only in their linear dimension
which is a positive integer not exceeding 1000000. A bag with smaller dimension
will fit in one with larger dimension. You are to compute which bags to pack within
which others so as to minimize the overall number of pieces of luggage
(i.e. the number of outermost bags). While maintaining the minimal number of
pieces you are also to minimize the total number of bags in any one piece that
must be carried.

Standard input contains several test cases. Each test case consists of an integer
*1 ≤ n ≤ 10000* giving the number of bags followed by *n* integers
on one or more lines,
each giving the dimension of a piece. A line containing 0 follows the last test
case. For each test case your output should consist of *k*, the minimum
number of pieces, followed by *k* lines, each giving the dimensions of the
bags comprising one piece, separated by spaces. Each dimension in the
input should appear exactly once in the output, and the bags in each piece must
fit nested one within another. If there is more than one solution, any will do. Output
an empty line between cases.

### Sample Input

6
1 1 2 2 2 3
0

### Output for Sample Input

3
1 2
1 2
3 2

*Troy Vasiga, Graeme Kemkes, Ian Munro, Gordon V. Cormack*