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 ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = int.Parse(Console.ReadLine());
            var str = Console.ReadLine();
            var strs = str.Split(' ');
            var a = new List<string>();
            var b = new List<string>();

            for (int i = 0; i < n; i++)
            {
                if (i % 2 == 0)
                {
                    a.Add(strs[i]);
                }
                else
                {
                    b.Add(strs[i]);
                }
            }

            var tableA = new Dictionary<string, int>();
            var tableB = new Dictionary<string, int>();
            foreach (var item in a)
            {
                if (tableA.ContainsKey(item))
                {
                    tableA[item]++;
                }
                else
                {
                    tableA.Add(item, 1);
                }
            }
            foreach (var item in b)
            {
                if (tableB.ContainsKey(item))
                {
                    tableB[item]++;
                }
                else
                {
                    tableB.Add(item, 1);
                }
            }

            var sortedA = tableA.OrderBy(x => x.Value);
            var sortedB = tableB.OrderBy(x => x.Value);
            var modeA = new string[2];
            var modeB = new string[2];
            var k = 0;
            foreach (var item in sortedA)
            {
                modeA[k] = item.Key;

                k++;
                if (k == 2) break;
            }

            k = 0;
            foreach (var item in sortedB)
            {
                modeB[k] = item.Key;

                k++;
                if (k == 2) break;
            }

            var hn = n / 2;
            if (modeA[0] != modeB[0])
            {
                var output = hn - tableA[modeA[0]] + hn - tableB[modeB[0]];
                Console.WriteLine(output);
                return;
            }

            if (tableA.Count == 1 && tableB.Count == 1)
            {
                Console.WriteLine(hn);
                return;
            }

            if (tableA.Count == 1)
            {
                Console.WriteLine(hn - tableB[modeB[1]]);
            }
            if (tableB.Count == 1)
            {
                Console.WriteLine(hn - tableB[modeA[1]]);
            }

            var cA = hn - tableA[modeA[0]] + hn - tableB[modeB[1]];
            var cB = hn - tableA[modeA[1]] + hn - tableB[modeB[0]];

            Console.WriteLine(cA < cB ? cA : cB);
        }
    }
}