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: Accepted)

io = STDIN
n=io.gets.to_i
V=io.gets.split.map(&:to_i)
even=Hash.new{|h,k|h[k]=0}
odd=Hash.new{|h,k|h[k]=0}
V.each_with_index do |v,i|
  if i.even?
    even[v]+=1
  else
    odd[v]+=1
  end
end
ev=even.sort_by{|h,v|v*-1}
od=odd.sort_by{|h,v|v*-1}
if ev.size==1 &&
   od.size==1
   if ev[0][0]==od[0][0]
     puts n/2
   else
     puts 0
   end
elsif ev.size==1 &&
   od.size!=1
   if ev[0][0]==od[0][0]
     puts n/2-od[1][1]
   else
     puts n/2-od[0][1]
   end
elsif ev.size!=1 &&
   od.size==1
   if ev[0][0]==od[0][0]
     puts n/2-ev[1][1]
   else
     puts n/2-ev[0][1]
   end
else
  if ev[0][0]==od[0][0]
    if ev[0][1]==od[0][1]
      if ev[1][1]==od[1][1]
        puts n-ev[0][1]-od[1][1]
      elsif ev[1][1]>od[1][1]
        puts n-ev[1][1]-od[0][1]
      else
        puts n-ev[0][1]-od[1][1]
      end
    elsif ev[0][1]>od[0][1]
      puts n-ev[0][1]-od[1][1]
    else
      puts n-ev[1][1]-od[0][1]
    end
  else
    puts n-ev[0][1]-od[0][1]
  end
end