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: Wrong Answer)

# frozen_string_literal: true

_ = gets.to_i
numbers = gets.split.map(&:to_i)

h1 = {}
h2 = {}
numbers.each_slice(2) {|pair|
  a = pair[0]
  b = pair[1]

  h1[a] ||= 0
  h2[b] ||= 0

  h1[a] = h1[a] + 1
  h2[b] = h2[b] + 1
}

answer =
  if h1.size == 1 && h2.size == 1
    if h1.keys[0] == h2.keys[0]
      h1.values[0]
    else
      0
    end
  else
    a = h1.size == 1 ? 0 : h1.values.sort[0...-1].inject(:+)
    b = h2.size == 1 ? 0 : h2.values.sort[0...-1].inject(:+)
    a + b
  end

puts answer