Problem:
Score : 400 points

Problem Statement

There are N pieces of sushi. Each piece has two parameters: "kind of topping" t_i and "deliciousness" d_i.
You are choosing K among these N pieces to eat.
Your "satisfaction" here will be calculated as follows:

The satisfaction is the sum of the "base total deliciousness" and the "variety bonus".

The base total deliciousness is the sum of the deliciousness of the pieces you eat.

The variety bonus is x*x, where x is the number of different kinds of toppings of the pieces you eat.

You want to have as much satisfaction as possible.
Find this maximum satisfaction.

Constraints

1 \leq K \leq N \leq 10^5

1 \leq t_i \leq N

1 \leq d_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
t_1 d_1
t_2 d_2
.
.
.
t_N d_N

Output

Print the maximum satisfaction that you can obtain.

Sample Input 1

5 3
1 9
1 7
2 6
2 5
3 1

Sample Output 1

26

If you eat Sushi 1,2 and 3:

The base total deliciousness is 9+7+6=22.

The variety bonus is 2*2=4.

Thus, your satisfaction will be 26, which is optimal.

Sample Input 2

7 4
1 1
2 1
3 1
4 6
4 5
4 5
4 5

Sample Output 2

25

It is optimal to eat Sushi 1,2,3 and 4.

Sample Input 3

6 5
5 1000000000
2 990000000
3 980000000
6 970000000
6 960000000
4 950000000

Sample Output 3

4900000016

Note that the output may not fit into a 32-bit integer type.

Solution in Ruby (2.3.3) (judge verdict: Runtime Error)

# とりあえず価値が最大になるように取ってみると、
# この種類より少ない状態で、最大値になることはないことが分かる
# なのであとは、今まで入っていなかった種類のうち最大のものから順番に置き換えていって、
# その中で、最大だったものを出力するだけ
tds = tds.sort_by{|td| td[1]*-1 }
selected = tds[0, K]
not_selected = tds[K, N]

current_kinds = Set.new(selected.map{|td| td[0] })
current_score = selected.map{|td| td[1] }.inject(:+)
max = current_score + current_kinds.size ** 2

dups_set = Set[]
dups_in_selected = []
selected.each do |td|
  t,d = td
  if dups_set.include? t
    dups_in_selected << td
  else
    dups_set << t
  end
end

if not_selected.nil?
  puts max
  exit
end

not_selected.each do |td|
  t,d = td
  next if current_kinds.include? t
  # remove duplicates, insert new kind
  removed = dups_in_selected.pop
  break if removed.nil?
  current_score -= removed[1]
  current_score += td[1]
  current_kinds << td[0]
  max = [max, current_score + current_kinds.size ** 2].max
end
puts max