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)

ary=$stdin.readlines
od=Array.new
ev=Array.new
n = ary[0].to_i
array=ary[1].split.map!(&:to_i)
p=0
while p<n
  od.push(array[p]) if p%2==0
  ev.push(array[p]) if p%2==1
  p+=1
end

  sd_n_ns_od = od.group_by{|i| i}.sort_by{|k,v| v.size}
  sd_n_ns_ev = ev.group_by{|i| i}.sort_by{|k,v| v.size}

if sd_n_ns_od.size == 1 && sd_n_ns_ev.size == 1
    answer = n/2
  else
most_n_od = sd_n_ns_od.last.first
most_n_ev = sd_n_ns_od.reject{|i| i== most_n_od}.last.first
answer1=0
answer1+=od.reject{|i| i==most_n_od}.size
answer1+=ev.reject{|i| i==most_n_ev}.size

most_n_ev = sd_n_ns_ev.last.first
most_n_od = sd_n_ns_ev.reject{|i| i== most_n_ev}.last.first
answer2=0
answer2+=ev.reject{|i| i==most_n_ev}.size
answer2+=od.reject{|i| i==most_n_od}.size

 answer = (answer1 <= answer2)?  (answer1):(answer2)
if  sd_n_ns_od[-2]  && sd_n_ns_ev[-2]
  if sd_n_ns_od.last.last.size == sd_n_ns_od[-2].last.size || sd_n_ns_ev.last.last.size == sd_n_ns_ev[-2].last.size
    answer=0
  answer+=od.reject{|i| i == sd_n_ns_od.last.first}.size
  answer+=ev.reject{|i| i == sd_n_ns_ev.last.first}.size
 end

 if  sd_n_ns_od.size == 1
   answer=answer1
 end

 if  sd_n_ns_ev.size == 1
   answer=answer2
 end
end
end
puts answer