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)

#! /usr/bin/env ruby

input = STDIN.read.split("\n").map{|l| l.split(" ").map{|i| i.to_i}}
d = input[1]

# even, odd のそれぞれの要素ごとの個数を数える

evens = {}
odds = {}

def countup(dic, v)
  if dic.has_key?(v) then
    dic[v] = dic[v] + 1
  else
    dic[v] = 1
  end
end

d.each_with_index do |v, i|
  if i % 2 == 1 then
    odds_cnt = odds_cnt
    countup(odds, v)
  else
    countup(evens, v)
  end
end

# それぞれの最大個数を持つ要素を取り出す
odds_max = odds.max{|x,y| x[1] <=> y[1]}
evens_max = evens.max{|x,y| x[1] <=> y[1]}

odds_max_v = odds_max[0]
odds_max_cnt = odds_max[1]
evens_max_v = evens_max[0]
evens_max_cnt = evens_max[1]

# もし、最大個数の要素が一致していたら、2番めに多い個数の要素を取り出す
if odds_max_v == evens_max_v then
  if odds_max_cnt > evens_max_cnt then
    evens.delete(evens_max_v)
    if evens.length == 0 then
      evens_max = [0,0]
    else
      evens_max = evens.max{|x,y| x[1] <=> y[1]}
    end
    evens_max_v = evens_max[0]
    evens_max_cnt = evens_max[1]
  else
    odds.delete(odds_max_v)
    if odds.length == 0 then
      odds_max = [0,0]
    else
      odds_max = odds.max{|x,y| x[1] <=> y[1]}
    end
    odds_max_v = odds_max[0]
    odds_max_cnt = odds_max[1]
  end
end

p d.length - evens_max_cnt - odds_max_cnt