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;

public class Program333
{
    public static void Main(string[] args)
    {
        var n = int.Parse(Console.ReadLine());

        var xy = Console.ReadLine().Split(' ');
        var f = new Dictionary<int, int>();
        var s = new Dictionary<int, int>();
        for (int i = 0; i < n; i=i+2)
        {
            var n1 = int.Parse(xy[i]);
            var n2 = int.Parse(xy[i+1]);
            if (f.ContainsKey(n1))
            {
                f[n1]++;  //todo
            }
            else
            {
                f.Add(n1, 1);
            }

            if (s.ContainsKey(n2))
            {
                s[n2]++;  //todo
            }
            else
            {
                s.Add(n2, 1);
            }
        }

        var maxN1Count = 0;
        var maxNum = 0;
        var maxN2Count = 0;
        foreach (var kv in f)
        {
            if (maxN1Count < kv.Value)
            {
                maxNum = kv.Key;
                maxN1Count = kv.Value;
            }
        }

        foreach (var kv in s)
        {
            if (kv.Key!= maxNum)
            {
                if (maxN2Count < kv.Value)
                {
                    maxN2Count = kv.Value;
                }

            }
        }

        var result = n - maxN1Count - maxN2Count;
        Console.WriteLine(result);


    } // Main
}     // Class