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.Text;

namespace Practice
{
    class Program
    {
        private static int ReadAndParseInt()
        {
            return int.Parse(Console.ReadLine());
        }
        private static int[] ReadAndParseIntArr()
        {
            return Array.ConvertAll(Console.ReadLine().Split(' '), int.Parse);
        }
        private static long ReadAndParseLong()
        {
            return long.Parse(Console.ReadLine());
        }
        private static long[] ReadAndParseLongArr()
        {
            return Array.ConvertAll(Console.ReadLine().Split(' '), long.Parse);
        }
        static void Main(string[] args)
        {
            SolveA(args);
            //SolveB(args);
            //SolveC(args);
            //SolveD(args);


        }
        static void SolveA(string[] args)
        {
            int n = ReadAndParseInt();
            var v = ReadAndParseIntArr();

            int ans = 0;
            int num0, total0;
            FindMost(v, 0, -1, out num0, out total0);
            ans = v.Length / 2 - total0;

            FindMost(v, 1, num0, out num0, out total0);
            ans += v.Length / 2 - total0;

            int ans1 = 0;
            FindMost(v, 1, -1, out num0, out total0);
            ans1 = v.Length / 2 - total0;

            FindMost(v, 0, num0, out num0, out total0);
            ans1 += v.Length / 2 - total0;

            ans = Math.Min(ans, ans1);
            Console.WriteLine(ans);
        }

        private static void FindMost(int[] v, int offset, int ignoreNum ,out int num,out int total)
        {
            var hash = new Dictionary<int, int>();// key 数値、value 個数
            for(int i=offset;i<v.Length;i+=2)
            {
                if(hash.ContainsKey(v[i])){
                    hash[v[i]]++;
                }else{
                    hash.Add(v[i], 1);
                }
            }
            num = -1;
            total = 0;
            foreach(var pair in hash)
            {
                if(pair.Value > total && pair.Key != ignoreNum)
                {
                    num = pair.Key;
                    total = pair.Value;
                }
            }
        }
    }
}