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.IO;
using System.Collections.Generic;
using System.Linq;

namespace ARC103C
{
    public class Program
    {
        struct Result
        {
            public int ReplaceCount;
            public int RemainNumber;
        }

        void Solve(StreamScanner ss, StreamWriter sw)
        {
            //---------------------------------
            var N = ss.Next(int.Parse);
            var V = ss.Next(int.Parse, N);
            var odds = V.Where((_, i) => i % 2 == 0);
            var evens = V.Where((_, i) => i % 2 == 1);

            var oddsRes = GetResult(odds);
            var evensRes = GetResult(evens);
            if (oddsRes.RemainNumber != evensRes.RemainNumber)
            {
                Console.WriteLine(oddsRes.ReplaceCount + evensRes.ReplaceCount);
                return;
            }

            var res1 = GetResult(odds, 0).ReplaceCount + GetResult(evens, 1).ReplaceCount;
            var res2 = GetResult(odds, 1).ReplaceCount + GetResult(evens, 0).ReplaceCount;
            Console.WriteLine(Math.Max(res1, res2));
            //---------------------------------
        }

        Result GetResult(IEnumerable<int> seq, int rank = 0)
        {
            var counts = new Dictionary<int, int> {{0, 0}};

            foreach (var x in seq)
            {
                if (!counts.ContainsKey(x)) counts.Add(x, 0);
                counts[x]++;
            }

            var remain = counts.OrderByDescending(pair => pair.Value).ToArray()[rank];
            return new Result{ReplaceCount = seq.Count() - remain.Value, RemainNumber = remain.Key};
        }

        static void Main()
        {
            var ss = new StreamScanner(new StreamReader(Console.OpenStandardInput()));
            var sw = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            new Program().Solve(ss, sw);
            sw.Flush();
        }

        static readonly Func<string, string> String = s => s;
    }

    public class StreamScanner
    {
        static readonly char[] Sep = {' '};
        readonly Queue<string> buffer = new Queue<string>();
        readonly TextReader textReader;

        public StreamScanner(TextReader textReader)
        {
            this.textReader = textReader;
        }

        public T Next<T>(Func<string, T> parser)
        {
            if (buffer.Count != 0) return parser(buffer.Dequeue());
            var nextStrings = textReader.ReadLine().Split(Sep, StringSplitOptions.RemoveEmptyEntries);
            foreach (var nextString in nextStrings) buffer.Enqueue(nextString);
            return Next(parser);
        }

        public T[] Next<T>(Func<string, T> parser, int x)
        {
            var ret = new T[x];
            for (var i = 0; i < x; ++i) ret[i] = Next(parser);
            return ret;
        }

        public T[][] Next<T>(Func<string, T> parser, int x, int y)
        {
            var ret = new T[y][];
            for (var i = 0; i < y; ++i) ret[i] = Next(parser, x);
            return ret;
        }
    }
}