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 System.IO;
using System.Text.RegularExpressions;
using System.Diagnostics;
using static System.Math;
using static System.Array;

//var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
namespace AtCoderSolve
{

    class Solve
    {
        const int mod = 1000000007;
        const int INF = 2147483647;
        const long SINF = 9223372036854775807;

        static int N;
        static int[] v;

        
        public static void Input()
        {
            var cin = new Solve();
            N = int.Parse(Console.ReadLine());
            v = cin.SplitReader();
        }

        static void Main(string[] args)
        {
            Input();
            //var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            //Console.SetOut(sw);

            if (v.Distinct().Count() == 1)
            {
                Console.WriteLine(N / 2);
                return;
            }
            int[] even = new int[N / 2];
            int[] odd = new int[N / 2];
            for(var i = 0; i < N; i++)
            {
                if (i % 2 == 0)
                {
                    even[i / 2] = v[i];
                }
                else
                {
                    odd[i / 2] = v[i];
                }
            }

            Sort(even);
            Sort(odd);
            List<Tuple<int, int>> E = new List<Tuple<int, int>>();
            List<Tuple<int, int>> O = new List<Tuple<int, int>>();

            int len = 1;
            for(var i = 0; i < N / 2; i++)
            {
                if (i == N / 2 - 1) { E.Add(new Tuple<int, int>(len, even[i])); }
                else
                {
                    if (even[i + 1] == even[i]) { len++; }
                    else
                    {
                        E.Add(new Tuple<int, int>(len, even[i]));
                        len = 1;
                    }
                }
            }
            len = 1;
            for (var i = 0; i < N / 2; i++)
            {
                if (i == N / 2 - 1) { O.Add(new Tuple<int, int>(len, odd[i])); }
                else
                {
                    if (odd[i + 1] == odd[i]) { len++; }
                    else
                    {
                        O.Add(new Tuple<int, int>(len, odd[i]));
                        len = 1;
                    }
                }
            }

            E.Sort((a, b) => (b.Item1 - a.Item1));
            O.Sort((a, b) => (b.Item1 - a.Item1));

            long ans = N;
            if (E[0].Item2 == O[0].Item2)
            {
                
                if (E.Count() == 1)
                {
                    ans -= E[0].Item1 + O[1].Item1;
                }
                else if (O.Count() == 1)
                {
                    ans -= E[1].Item1 + O[0].Item1;
                }
                else
                {
                    ans = Min(ans - E[0].Item1 - O[1].Item1, ans - E[1].Item1 - O[0].Item1);
                }
            }
            else
            {
                ans -= E[0].Item1 + O[0].Item1;
            }

            Console.WriteLine(ans);

            //Console.Out.Flush();
        }

        public int[] SplitReader()
        {
            int[] array = Console.ReadLine().Split().Select(int.Parse).ToArray();
            return array;
        }
        public long[] SplitReaderL()
        {
            long[] array = Console.ReadLine().Split().Select(long.Parse).ToArray();
            return array;
        }

    }
}