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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace C_VVV
{
    class Program
    {
        static void Main(string[] args)
        {            
            string str1 = Console.ReadLine();
            int n = int.Parse(str1);
            string[] str2 = Console.ReadLine().Split(' ');
            int[] v = new int[n];
            for(int i = 0; i < n; i++)
            {
                v[i] = int.Parse(str2[i]);
            }

            List<int> list = new List<int>();
            
            for(int i = 0; i < n; i++)
            {
                if (!list.Contains(v[i]))
                {
                    list.Add(v[i]);
                }
            }

            int[] a = new int[n];
            int result = int.MaxValue;
            
            
            for(int i = 0; i < list.Count; i++)
            {
                if (list.Count == 1)
                {
                    break;
                }
                for(int j = 0; j < list.Count-1; j++)
                {
                    if (i != j)
                    {
                        for (int k = 0; k < n; k++)
                        {
                            //奇数番目
                            if (k % 2 == 1)
                            {
                                a[k] = list[i];
                            }
                            //偶数番目
                            else
                            {
                                a[k] = list[j];
                            }
                        }

                        int changeNum = 0;
                        
                        for(int k = 0; k < n; k++)
                        {
                            if (a[k] != v[k])
                            {
                                changeNum++;
                            }
                        }

                        if (changeNum < result)
                        {
                            result = changeNum;
                        }

                    }
                   
                }
            }
            result = n / 2;

            Console.Write(result);
           
        }
    }
}