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;

namespace AtCoder.ARC._103
{
    class c
    {
        static Dictionary<int, int> odd = new Dictionary<int, int>();
        static Dictionary<int, int> even = new Dictionary<int, int>();

        static void Main(string[] args)
        {
            var line = Console.ReadLine().Trim();
            var N = int.Parse(line);
            line = Console.ReadLine().Trim();
            var A = Array.ConvertAll(line.Split(' '), new Converter<string, int>(s => int.Parse(s)));
            for(var i = 0; i < N; ++i)
            {
                if(i % 2 == 0)
                {
                    if (odd.ContainsKey(A[i]))
                    {
                        odd[A[i]]++;
                    }
                    else
                    {
                        odd.Add(A[i], 1);
                    }
                }
                else
                {
                    if (even.ContainsKey(A[i]))
                    {
                        even[A[i]]++;
                    }
                    else
                    {
                        even.Add(A[i], 1);
                    }
                }
            }
            var oddList = searchPair(odd);
            var evenList = searchPair(even);
            if(oddList[0].Item1 != evenList[0].Item1)
            {
                Console.WriteLine(N - oddList[0].Item2 - evenList[0].Item2);
            }
            else
            {
                if(oddList.Count == 1 || evenList.Count == 1)
                {
                    if(oddList.Count == 1 && evenList.Count == 1)
                    {
                        Console.WriteLine(N / 2);
                    }
                    else if (oddList.Count == 1)
                    {
                        Console.WriteLine(N / 2 - evenList[1].Item2);
                    }
                    else
                    {
                        Console.WriteLine(N / 2 - oddList[1].Item2);
                    }
                }
                else
                {
                    var oddN1 = oddList[0].Item2;
                    var oddN2 = oddList[1].Item2;
                    var evenN1 = oddList[0].Item2;
                    var evenN2 = oddList[1].Item2;
                    Console.WriteLine(N - (oddN1 + evenN2 > oddN2 + evenN1 ? oddN1 + evenN2 : oddN2 + evenN1));
                }
            }
        }


        private static List<Tuple<int,int>> searchPair(Dictionary<int, int> list)
        {
            List<Tuple<int, int>> t = new List<Tuple<int, int>>();
            foreach(var k in list.Keys)
            {
                t.Add(new Tuple<int, int>(k, list[k]));
            }
            t.Sort((x,y) => x.Item2 - y.Item2);
            return t;
        }
    }
}