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;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Linq;
using System.Diagnostics;
using System.Globalization;
using static System.Console;
using static System.Math;

namespace abc111_c
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] input = ReadLine().Split().Select(int.Parse).ToArray();
            var dic1 = new Dictionary<int,int>();
            var dic2 = new Dictionary<int,int>();

            for (int i = 1; i < n; i+=2){
                if(dic1.ContainsKey(input[i-1])) dic1[input[i-1]]++;
                else dic1[input[i-1]] = 1;

                if(dic2.ContainsKey(input[i])) dic2[input[i]]++;
                else dic2[input[i]] = 1;
            }

            Array.Sort(input);
            if(input[0] == input[n-1]){
                WriteLine(n/2);
            }else{
                var tmp1 = dic1.OrderBy((x) => x.Value).OrderByDescending((x) => x.Value).ToList();
                var tmp2 = dic2.OrderBy((x) => x.Value).OrderByDescending((x) => x.Value).ToList();

                if(tmp1[0].Key == tmp2[0].Key){
                    if(tmp1[0].Value < tmp2[0].Value){
                        WriteLine(n-tmp1[1].Value-tmp2[0].Value);
                    } else {
                        WriteLine(n-tmp1[0].Value-tmp2[1].Value);
                    }
                }else{
                    WriteLine(n-tmp1[0].Value-tmp2[0].Value);
                }
            }
        }
    }
}