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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class AtCoderA
{
    static void Main()
    {
        var sc = new Scanner();

        long n = sc.NextLong();
        long[] v = sc.LongArray();

        Dictionary<long, long> oddDic = new Dictionary<long, long>();
        Dictionary<long, long> evenDic = new Dictionary<long, long>();

        for (int i = 0; i < n; i++)
        {
            if (i % 2 == 0)
            {
                if (evenDic.ContainsKey(v[i]))
                {
                    evenDic[v[i]]++;
                }
                else
                {
                    evenDic.Add(v[i], 1);
                }
            }
            else
            {
                if (oddDic.ContainsKey(v[i]))
                {
                    oddDic[v[i]]++;
                }
                else
                {
                    oddDic.Add(v[i], 1);
                }
            }
        }

        var oddList = oddDic.OrderByDescending(i => i.Value).ToList();
        var evenList = evenDic.OrderByDescending(i => i.Value).ToList();

        var oddMax = oddList[0].Value;
        var evenMax = evenList[0].Value;

        if (oddList[0].Key == evenList[0].Key)
        {
            if (oddList.Count == 1 && evenList.Count == 1)
            {
                evenMax = 0;
            }
            else if (oddList.Count == 1)
            {
                evenMax = evenList[1].Value;
            }
            else if (evenList.Count == 1)
            {
                oddMax = oddList[1].Value;
            }
            else
            {
                if (oddList[1].Value > evenList[1].Value)
                {
                    oddMax = oddList[1].Value;
                }
                else
                {
                    evenMax = evenList[1].Value;
                }
            }
        }

        long answer = n - oddMax - evenMax;

        Console.WriteLine(answer);
    }

    class Scanner
    {
        private string[] _line;
        private int _index;
        private const char Separator = ' ';

        public Scanner()
        {
            _line = new string[0];
            _index = 0;
        }

        public string Next()
        {
            while (_index >= _line.Length)
            {
                _line = Console.ReadLine().Split(Separator);
                _index = 0;
            }

            return _line[_index++];
        }

        public int NextInt() => int.Parse(Next());
        public long NextLong() => long.Parse(Next());
        public double NextDouble() => double.Parse(Next());
        public decimal NextDecimal() => decimal.Parse(Next());
        public char NextChar() => Next()[0];
        public char[] NextCharArray() => Next().ToCharArray();

        public string[] Array()
        {
            _line = Console.ReadLine().Split(Separator);
            _index = _line.Length;
            return _line;
        }

        public int[] IntArray() => Array().Select(int.Parse).ToArray();
        public long[] LongArray() => Array().Select(long.Parse).ToArray();
        public double[] DoubleArray() => Array().Select(double.Parse).ToArray();
        public decimal[] DecimalArray() => Array().Select(decimal.Parse).ToArray();
    }
}