Problem:
Score : 300 points

Problem Statement

A sequence a_1,a_2,... ,a_n is said to be /\/\/\/ when the following conditions are satisfied:

For each i = 1,2,..., n-2, a_i = a_{i+2}.

Exactly two different numbers appear in the sequence.

You are given a sequence v_1,v_2,...,v_n whose length is even.
We would like to make this sequence /\/\/\/ by replacing some of its elements.
Find the minimum number of elements that needs to be replaced.

Constraints

2 \leq n \leq 10^5

n is even.

1 \leq v_i \leq 10^5

v_i is an integer.

Input

Input is given from Standard Input in the following format:

n
v_1 v_2 ... v_n

Output

Print the minimum number of elements that needs to be replaced.

Sample Input 1

4
3 1 3 2

Sample Output 1

1

The sequence 3,1,3,2 is not /\/\/\/, but we can make it /\/\/\/ by replacing one of its elements: for example, replace the fourth element to make it 3,1,3,1.

Sample Input 2

6
105 119 105 119 105 119

Sample Output 2

0

The sequence 105,119,105,119,105,119 is /\/\/\/.

Sample Input 3

4
1 1 1 1

Sample Output 3

2

The elements of the sequence 1,1,1,1 are all the same, so it is not /\/\/\/.

Solution in Ruby (2.3.3) (judge verdict: Accepted)

# https://atcoder.jp/contests/abc111/tasks/arc103_a


n = gets.to_i
vs = gets.split.map(&:to_i)

as, bs = vs.each_slice(2).to_a.transpose.map do |ws|
  ws
  .group_by(&:itself)
  .map { |k, vs| [vs.size, k] }
  .group_by { |c, k| c }
  .sort
  .reverse
  .take(2)
  .map { |c, vs| [c, vs.transpose[1].sort] }
  .push([0, []])
end

keep = (
  if as[0][1].size > 1 || bs[0][1].size > 1 || as[0][1] != bs[0][1]
    as[0][0] + bs[0][0]
  else
    [as[0][0] + bs[1][0], as[1][0] + bs[0][0]].max
  end
)

puts n - keep