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 static System.Console;
using static System.Math;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Solve.Answer();
            }
            catch (Exception ex)
            {
                WriteLine(ex.ToString());
            }
        }
    }

    public class Solve
    {
        public static void Answer()
        {
            var N = IO_ShortCut.ReadInt;
            var V = IO_ShortCut.ReadSplitInt;

            var V_Odd = V.Where((v, idx) => idx % 2 == 0).ToList();
            var V_Even = V.Where((v, idx) => idx % 2 == 1).ToList();

            var Odd = V_Odd.GroupBy(v => v).ToDictionary(v => v.Key, v => v.Count());
            Odd.OrderByDescending(x => x.Value);
            var Even = V_Even.GroupBy(v => v).ToDictionary(v => v.Key, v => v.Count());
            Even.OrderByDescending(x => x.Value);
            int ans = 0;
            if (Odd.First().Key != Even.First().Key)
            {
                ans = N - Odd.First().Value - Even.First().Value;
            }
            else
            {
                if (Odd.Where((x, idx) => idx == 1).ToDictionary(x => x.Key, x => x.Value).First().Key
                    == Even.Where((x, idx) => idx == 1).ToDictionary(x => x.Key, x => x.Value).First().Key)
                    ans = N - Odd.First().Value - Even[Even.Where((x, idx) => idx == 1).ToDictionary(x => x.Key, x => x.Value).First().Key];
                else
                    ans = N - Odd.First().Value - Min(Odd[Odd.Where((x, idx) => idx == 1).ToDictionary(x => x.Key, x => x.Value).First().Key],
                        Even[Even.Where((x, idx) => idx == 1).ToDictionary(x => x.Key, x => x.Value).First().Key]);
            }
            WriteLine(ans);
        }
    }

    public class IO_ShortCut
    {
        #region Input
        public static string ReadString => ReadLine();
        public static int ReadInt => int.Parse(ReadLine());
        public static long ReadLong => long.Parse(ReadLine());
        public static double ReadDouble => double.Parse(ReadLine());

        public static List<string> ReadSplitString => ReadLine().Split().ToList();
        public static List<int> ReadSplitInt => ReadLine().Split().Select(s => int.Parse(s)).ToList();
        public static List<long> ReadSplitLong => ReadLine().Split().Select(s => long.Parse(s)).ToList();
        public static List<double> ReadSplitdouble => ReadLine().Split().Select(s => double.Parse(s)).ToList();
        #endregion

        #region Output
        public static void OutJoinSpace<T>(IEnumerable<T> list) => WriteLine(string.Join(" ", list));
        public static void WriteLineYes_or_No(bool flag) => WriteLine(flag ? "Yes" : "No");

        #endregion
    }

    /// <summary>
    /// 正の数の四則演算のみ対応
    /// </summary>
    public class Mod
    {
        // 割る数の定義
        private readonly static long M = 1000000007;

        // 足し算
        public static long Add(long a, long b) => (a * b) % M;
        // 引き算
        public static long Sub(long a, long b) => (a - b) % M >= 0 ? (a - b) % M : (a - b) % M + M;
        // 掛け算
        public static long Multi(long a, long b) => (a * b) % M;
    }

    public class MathLib
    {
    }
}