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)

def checkall(even, odd)
  input_ary = even + odd
  input_ary.uniq.length == 1
end
def ok?(ary)
  ary.uniq.length == 1
end
def modify(ary, count)
  data = {}
  sorted = ary.sort()
  sorted.each do |val|
    unless data.include? val
      data[val] = 1
    else
      data[val] += 1
    end
  end
  max_count_value, max_count = data.sort {|(cur_key, cur_val), (nxt_key, nxt_val)|
    cur_val <=> nxt_val
  }.reverse[0]
  count += (ary.length - max_count)
  return count
end
n = gets.chomp!.to_i
ary = gets.chomp!.split(' ').map(&:to_i)
count = 0
even = ary.select.with_index{ |_, idx| idx % 2 == 0 }
odd = ary.select.with_index{ |_, idx| idx % 2 != 0 }
if checkall(even, odd)
  count += [even.length, odd.length].min
  puts count
else
  if ok?(even) && ok?(odd)
    puts count
  elsif ok?(even)
    count += modify(odd, count)
    puts count
  elsif ok?(odd)
    count += modify(even, count)
    puts count
  else
    count += modify(odd, count)
    count = modify(even, count)
    puts count
  end
end