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: Time Limit Exceeded)

using System;
using System.Collections.Generic;

class Program
{

    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        string[] array = Console.ReadLine().Split(' ');
        int[] v = new int[n];
        int[] e = new int[n / 2];
        int[] o = new int[n / 2];
        for (int i = 0; i < array.Length; i++)
        {
            v[i] = int.Parse(array[i]);
            if (i % 2 == 0) e[i / 2] = int.Parse(array[i]);
            else o[i / 2] = int.Parse(array[i]);
        }

        int e1 = Mode(e);
        int o1 = Mode(o);

        if (e1 == o1)
        {
            int e2 = Mode2nd(e, e1);
            int o2 = Mode2nd(o, o1);
            List<int> list_e1 = new List<int>(e);
            List<int> list_e2 = new List<int>(e);
            list_e1.RemoveAll(i => i == e1);
            list_e2.RemoveAll(i => i == e2);
            List<int> list_o1 = new List<int>(o);
            List<int> list_o2 = new List<int>(o);
            list_o1.RemoveAll(i => i == o1);
            list_o2.RemoveAll(i => i == o2);
            if ((list_e1.Count + list_o2.Count) < (list_e2.Count + list_o1.Count)) Console.WriteLine(list_e1.Count + list_o2.Count);
            else Console.WriteLine(list_e2.Count + list_o1.Count);
        }
        else
        {
            List<int> list_e = new List<int>(e);
            list_e.RemoveAll(i => i == e1);
            List<int> list_o = new List<int>(o);
            list_o.RemoveAll(i => i == o1);
            Console.WriteLine(list_e.Count + list_o.Count);
        }
    }

    static int Mode(int[] array)
    {
        int ans = -1;
        for (int i = 0; i < array.Length; i++)
        {
            int tmp = 0, mode = 0;
            for (int j = 0; j < array.Length; j++)
            {
                if (array[i] == array[j]) tmp++;
            }
            if (tmp > mode)
            {
                mode = tmp;
                ans = array[i];
            }
        }
        return ans;
    }

    static int Mode2nd(int[] array, int exc)
    {
        List<int> list = new List<int>(array);
        list.RemoveAll(i => i == exc);
        array = list.ToArray();

        int ans = -1;
        for (int i = 0; i < array.Length; i++)
        {
            int tmp = 0, mode = 0;
            for (int j = 0; j < array.Length; j++)
            {
                if (array[i] == array[j]) tmp++;
            }
            if (tmp > mode)
            {
                mode = tmp;
                ans = array[i];
            }
        }
        return ans;
    }
}