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 gs() STDIN.gets.chomp end
def gi() gets.to_i end
def gsmi() gets.chomp.split.map(&:to_i) end
 
def desc(ar) ar.sort!{|x,y|y<=>x} end
def min(a,b) a<=b ? a : b end
def max(a,b) a>=b ? a : b end
def sum(ar) ar.inject(:+) end

n = gi

vs = gsmi

max = [[[0,0],[0,0]],[[0,0],[0,0]]] #偶奇-１番-k,v

hs = Array.new(2){ Hash.new(0) }

vs.each.with_index{|v,i| hs[i%2][v] += 1 }

2.times do |i|
	hs[i].each  do |k,v|
		if max[i][0][1]<=v
			max[i][0][1], max[i][1][1] = v,max[i][0][1]
			max[i][0][0], max[i][1][0] = k,max[i][0][0]
		end
	end
end

if max[0][0][0]==max[1][0][0] && !(max[0][0][1]==max[0][1][1]||max[1][0][1]==max[1][1][1])
	if (max[0][0][1]-max[0][1][1])<(max[1][0][1]-max[1][1][1])
		max[0][0][1] = max[0][1][1]
	else
		max[1][0][1] = max[1][1][1]
	end
end

puts n-max[0][0][1]-max[1][0][1]