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)

def func(even_a, odd_a)
  e0 = even_a[0][1]
  e1 = (1 < even_a.length) ? even_a[1][1]: 0

  d0 = even_a[0][1]
  d1 = (1 < odd_a.length) ? odd_a[1][1]: 0

  r = [e0 + d1, e1 + d0].max
  return r
end

n = gets.chomp.to_i
t = gets.chomp.split(' ').map {|i| i.to_i}
even = {}
odd = {}
t.length.times do |i|
  k = t[i]
  if (i + 1) % 2 == 0
    # even
    if even[k]
      even[k] += 1
    else
      even[k] = 1
    end
  else
    # odd
    if odd[k]
      odd[k] += 1
    else
      odd[k] = 1
    end
  end
end

even_a = even.to_a
odd_a = odd.to_a
even_a.sort! {|a, b| (-1) * (a[1] <=> b[1])}
odd_a.sort! {|a, b| (-1) * (a[1] <=> b[1])}

m = 0
if even_a[0][0] != odd_a[0][0]
  m = even_a[0][1] + odd_a[0][1]
else
  m = func(even_a, odd_a)
  if m == 0
    m = t.length / 2
  end
end

r = t.length - m
puts r