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.to_i
a = gets.split.map(&:to_i)
od, ev = {}, {}

if a.uniq.size==1
  p N/2
  exit
end

a.select.with_index{|_,i| i.even?}.each do |n|
  if ev.key?(n)
    ev[n] += 1 
  else
    ev[n] = 1
  end
end

a.select.with_index{|_,i| i.odd?}.each do |n|
  if od.key?(n)
    od[n] += 1 
  else
    od[n] = 1
  end
end

evmx = ev.max_by{|k,v| v}
odmx = od.max_by{|k,v| v}

if evmx[0] == odmx[0]
  evs = ev.select{|k,v| v == evmx[1]}
  ods = od.select{|k,v| v == odmx[1]}
  
  if evs.size > ods.size
    ev.delete(odmx[0])
  else
    od.delete(evmx[0])
  end
end

p N - ev.max_by{|k,v| v}[1] - od.max_by{|k,v| v}[1]