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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Collections.Generic;

public class Hello
{
    static void Main()
    {
        int num = int.Parse(Console.ReadLine());
        string[] s_data = Console.ReadLine().Trim().Split(' ');

        int[] data = new int[s_data.Length];

        List<int> odd_array = new List<int>();
        List<int> even_array = new List<int>();

        int result = 0;

        for (int i = 0; i < s_data.Length; i++)
        {
            data[i] = int.Parse(s_data[i]);
            if (i % 2 == 0)
            {
                even_array.Add(data[i]);
            }
            else
            {
                odd_array.Add(data[i]);
            }
        }

        if (odd_array.SequenceEqual(even_array))
        {
            result = 2;
        }
        else
        { 
            var exclusionOddNum = odd_array.Distinct();
            var exclusionEvenNum = even_array.Distinct();

            result = exclusionEvenNum.Count() + exclusionOddNum.Count() - 2;
        }

        Console.WriteLine(result);
    }
}