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.Linq;
using System.Collections.Generic;
using static System.Console;
using System.Text;
using System.IO;
using static System.Math;
namespace AtCoder
{
    class Program
    {
        static public long[] Sarray() { return ReadLine().Split().Select(long.Parse).ToArray(); }
        static public List<long> Slist() { return ReadLine().Split().Select(long.Parse).ToList(); }

        static long Mod = (long)1e9 + 7;
        static void Main(string[] args)
        {
            //SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
            var N = Sarray()[0];
            var Vi = Sarray();
            if (1 == Vi.Distinct().Count())
            {
                WriteLine(N / 2);
                return;
            }
            var odd = new Dictionary<long, long>();
            var even = new Dictionary<long, long>();
            for (var i = 0; i < N; i += 2)
            {
                if (!odd.ContainsKey(Vi[i])) odd[Vi[i]] = 0;
                ++odd[Vi[i]];
                if (!even.ContainsKey(Vi[i + 1])) even[Vi[i + 1]] = 0;
                ++even[Vi[i + 1]];
            }
            var sodd = odd.OrderByDescending(o => o.Value).ToList();
            var seven = even.OrderByDescending(e => e.Value).ToList();
            var max = sodd[0].Value + seven[0].Value;
            if (sodd[0].Key == seven[0].Key)
            {
                if (sodd.Count == 1)
                    max = sodd[0].Value + seven[1].Value;
                else if (seven.Count == 1)
                    max = sodd[1].Value + seven[0].Value;
                else
                    max = Max(sodd[0].Value + seven[1].Value, sodd[1].Value + seven[0].Value);
            }
            WriteLine(N - max);
            //Out.Flush();
        }
    }
}