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)

n = gets.chomp.to_i
v = gets.chomp.split(" ").map(&:to_i)
evens = []
odds = []
v.each.with_index(1) do |e, i|
  if i % 2 == 0
    evens.push(e)
  else
    odds.push(e)
  end
end
def stats(arr)
  tmp = {}
  arr.each do |v|
    if tmp[v.to_s].nil?
      tmp[v.to_s] = 1
    else
      tmp[v.to_s] += 1
    end
  end
  tmp
end
evens_stats = stats(evens).sort.to_h
odds_stats = stats(odds).sort.to_h

even_best_count = evens_stats.values.first
even_best_number = evens_stats.keys.first
odd_best_count = odds_stats.values.first
odd_best_number = odds_stats.keys.first

if odd_best_number != even_best_number
  res = n - even_best_count - odd_best_count
else
  odd_best_count2 = odds_stats.values[1] || 0
  even_best_count2 = evens_stats.values[1] || 0
  res = [n - even_best_count - odd_best_count2, 
    n - even_best_count2 - odd_best_count].min
end
print("#{res}\n")