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.Text.RegularExpressions;
using System.Collections;

namespace SummerVacation
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.ReadLine();
            string[] tmpstr=Regex.Split(Console.ReadLine(), @"\s+");
         
            Hashtable ht1 = new Hashtable();
            Hashtable ht2 = new Hashtable();

            for (int i = 0; i < tmpstr.Length; i += 2)
            {
                HashTableMake(ref ht1, tmpstr[i]);
                HashTableMake(ref ht2, tmpstr[i + 1]);   
            }

            while (true)
            {
                int Topnum = 0, Topnum2 = 0;
                string Indexnum = "", Indexnum2 = "";
                int tmpht1 = 0, tmpht2 = 0;
                bool flag;

                HaTa(ref ht1, ref Topnum, ref Indexnum, ref tmpht1);
                HaTa(ref ht2, ref Topnum2, ref Indexnum2, ref tmpht2);

                if (!(Indexnum == Indexnum2))
                {
                    Console.WriteLine(tmpstr.Length - Topnum - Topnum2);
                    break;
                }
                else
                {
                    if (tmpht1 == 0 && tmpht2 == 0)
                    {
                        Console.WriteLine(tmpstr.Length / 2);
                        break;
                    }
                    else if (Topnum+tmpht2 > Topnum2 + tmpht1 || tmpht1==0)
                    {
                        flag = true;
                    }
                    else if (Topnum + tmpht2 < Topnum2 + tmpht1 || tmpht2==0)
                    {
                        flag = false;
                    }
                    else
                    { 
                        if (tmpht1 > tmpht2)
                            flag = false;
                        else if (tmpht1 == tmpht2)
                        {
                            if (Topnum > Topnum2)
                                flag = false;
                            else
                                flag = true;
                        }
                        else
                            flag = true;
                    }
                }
                if (flag)
                    ht2.Remove(Indexnum2);
                else
                    ht1.Remove(Indexnum);
            }
        }

        public static void HaTa(ref Hashtable ht1, ref int Topnum,ref string Indexnum,ref int tmpht1)
        {
            foreach (DictionaryEntry x in ht1)
            {
                if (Topnum < (int)x.Value)
                    tmpht1 = Topnum;
                    Topnum = (int)x.Value;
                    Indexnum = (string)x.Key;
            }
        }

        public static void HashTableMake(ref Hashtable ht,string tmpstr)
        {
            if (ht.ContainsKey(tmpstr))
                ht[tmpstr] = (int)ht[tmpstr] + 1;
            else
                ht[tmpstr] = 1;
        }
    }
}