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;


class Program
{
    static int e1 = -1;
    static int e1_n = 0;
    static int e2 = -1;
    static int e2_n = 0;
    static int o1 = -1;
    static int o1_n = 0;
    static int o2 = -1;
    static int o2_n = 0;

    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        string[] array = Console.ReadLine().Split();
        int[] v = new int[n];
        int[] e = new int[n / 2];
        int[] o = new int[n / 2];
        for (int i = 0; i < array.Length; i++)
        {
            v[i] = int.Parse(array[i]);
            if (i % 2 == 0) e[i / 2] = int.Parse(array[i]);
            else o[i / 2] = int.Parse(array[i]);
        }

        Mode(e, true);
        Mode(o, false);

        if (n == 2)
        {
            if (v[0] == v[1]) Console.WriteLine(1);
            else Console.WriteLine(0);
        }

        if (e1 == o1)
        {
            Console.WriteLine(Math.Min(e.Length - e1_n + o.Length - o2_n, e.Length - e2_n + o.Length - o1_n));
        }
        else
        {
            Console.WriteLine(e.Length - e1_n + o.Length - o1_n);
        }
    }

    //最頻値の個数を返す。flag = trueなら偶数用
    static void Mode(int[] array, bool flag)
    {
        int[] line = new int[100001];

        for (int i = 0; i < array.Length; i++)
        {
            line[array[i]]++;
        }

        if (flag)
        {
            for (int i = 1; i < line.Length; i++)
            {
                if (e1 < line[i])
                {
                    e1 = i;
                    e1_n = line[i];
                }
                else if (e2 <= line[i])
                {
                    e2 = i;
                    e2_n = line[i];
                }
            }
        }
        else
        {
            for (int i = 1; i < line.Length; i++)
            {
                if (o1 < line[i])
                {
                    o1 = i;
                    o1_n = line[i];
                }
                else if (o2 <= line[i])
                {
                    o2 = i;
                    o2_n = line[i];
                }
            }
        }
        return;
    }
}