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: Wrong Answer)

require 'set'
INF = 1 << 60

N, K = gets.split(' ').map(&:to_i)
td_list = N.times.map { gets.split(' ').map(&:to_i) }

def score(t_to_dlist)
  t_to_dlist.reduce(0) { |acc, (_, dlist)| acc + dlist.reduce(&:+) } +
  t_to_dlist.keys.size ** 2
end

def t_of_min_d(t_to_dlist)
  target_t = nil
  min = INF
  t_to_dlist.each do |(t, dlist)|
    next unless dlist.size >= 2
    d = dlist.last
    if d < min
      min = d
      target_t = t
    end
  end
  target_t
end

sorted_td_list = td_list.sort_by { |(_, d)| -d }
t_to_dlist =
  sorted_td_list.take(K).group_by(&:first).map do |(t, td_list)|
    [t, td_list.map { |(_, d)| d } ]
  end.to_h
t_set = Set.new(t_to_dlist.keys)
rest_sorted_td_list = sorted_td_list.drop(K)

max_score = score(t_to_dlist)
current_score = max_score
while t_set.count < K && rest_sorted_td_list.size > 0
  t, d = rest_sorted_td_list.shift
  next if t_set.include?(t)
  t2 = t_of_min_d(t_to_dlist)
  break unless t2
  t_set.add(t)
  dlist = t_to_dlist[t2]
  d2 = dlist.pop
  if dlist.empty?
    t_to_dlist.delete(t2)
    t_set.delete(t2)
  end
  t_to_dlist[t] = [d]
  new_score = current_score + (d + (t_set.size ** 2)) - (d2 + ((t_set.size - 1) ** 2))
  max_score = new_score if max_score < new_score
end
puts max_score