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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using static System.Console;
using static System.Convert;
using static System.Math;
//using static System.Globalization.CultureInfo;

class Program
{
    static void Main(string[] args)
    {
        var num = ToInt32(ReadLine());
        var v = Array.ConvertAll(ReadLine().Split(' '), int.Parse);
        var dic = new Dictionary<int, int>[2];
        dic[0] = new Dictionary<int, int>();
        dic[1] = new Dictionary<int, int>();
        for (var i = 0; i < num; i++)
            if (dic[i % 2].ContainsKey(v[i])) dic[i % 2][v[i]]++;
            else dic[i % 2][v[i]] = 1;
        for (var i = 0; i < 2; i++)
            dic[i] = dic[i].OrderByDescending(p => p.Value).ToDictionary(p => p.Key, p => p.Value);

        var ind0 = 0;
        var ind1 = 0;
        while (true)
        {
            var d0 = dic[0].Skip(ind0).FirstOrDefault();
            var d1 = dic[1].Skip(ind1).FirstOrDefault();
            if (d0.Key != d1.Key)
            {
                WriteLine(num - d0.Value - d1.Value);
                return;
            }
            else if (d0.Value == d1.Value)
            {
                WriteLine(num - d0.Value - Max(dic[0].Skip(ind0 + 1).FirstOrDefault().Value, dic[1].Skip(ind1 + 1).FirstOrDefault().Value));
                return;
            }
            else if (d0.Value > d1.Value)
                ind1++;
            else ind0++;
        }
    }
    private const string ALFA = "abcdefghijklmnopqrstuvwxyz";
    private const int MOD = 1000000007;
}