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: Runtime Error)

n = gets.chop.to_i
v = gets.chop.split.map(&:to_i)

odd = v.each_slice(2).map{|n| n.first}
even = v.each_slice(2).map{|n| n.last}

def num_of_elem(array)
  h = Hash.new{0}
  array.each do |key|
    h[key] += 1
  end
  h
end

odd_count = num_of_elem(odd)
even_count = num_of_elem(even)

odd_sorted = odd_count.to_a.sort_by{ |x| x[1]}.reverse
even_sorted = even_count.to_a.sort_by{ |x| x[1]}.reverse

if odd == even
  puts n/2
elsif odd_sorted[0][1] == n/2 && even_sorted[0][1] == n/2
  puts 0
else
  ans1 = n - odd_sorted[0][1] - even_sorted[1][1]
  ans2 = n - even_sorted[0][1] - even_sorted[1][1]

  puts [ans1, ans2].min
end