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 E = System.Linq.Enumerable;

public class Program
{
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine());
        var vs = Console.ReadLine().Split().Select(x => int.Parse(x)).ToArray();

        const int size = 1 + (int)1e5;
        var bucket = new [] { new int[size], new int[size] };
        for (int i = 0; i < vs.Length; i++)
        {
            bucket[i % 2][vs[i]]++;
        }
        var vss = new [] { new int[2], new int[2] };
        var kss = new [] { new int[2], new int[2] };
        for (int i = 0; i < bucket.Length; i++)
        {
            for (int j = 0; j < bucket[i].Length; j++)
            {
                if (bucket[i][j] <= kss[i][1])
                {
                    continue;
                }

                int k = 1;
                if (bucket[i][j] > kss[i][0])
                {
                    vss[i][1] = vss[i][0];
                    kss[i][1] = kss[i][0];
                    k = 0;
                }
                vss[i][k] = j;
                kss[i][k] = bucket[i][j];
            }
        }
        if (vss[0][0] == vss[1][0])
        {
            int i = kss[0][1] < kss[1][1] ? 1 : 0;
            kss[i][0] = kss[i][1];
        }
        Console.WriteLine(n - kss[0][0] - kss[1][0]);
    }
}