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 void Main(string[] args)
    {
        var n = int.Parse(Console.ReadLine());
        var s = Console.ReadLine().Split(' ');
        var v = new int[n];
        var even = new int[100001];
        var odd = new int[100001];

        for(var i = 0; i < n; i++)
        {
            if (i % 2 == 0)
            {
                v[i] = int.Parse(s[i]);
                even[v[i]]++;
            } else
            {
                v[i] = int.Parse(s[i]);
                odd[v[i]]++;
            }
        }

        int e1 = 0, e2 = 0, o1 = 0, o2 = 0;
        for (var i = 0; i < 100001; i++)
        {
            if (odd[i] > odd[e1])
            {
                o2 = o1;
                o1 = i;
            } else if (odd[i] > odd[e2])
            {
                e2 = i;
            }

            if (even[i] > even[e1])
            {
                e2 = e1;
                e1 = i;
            } else if (even[i] > even[e2])
            {
                e2 = i;
            }
        }

        if (e1 == o1)
        {
            Console.WriteLine(Math.Min(n - even[e1] - odd[o2], n - even[e2] - odd[01]));
        } else
        {
            Console.WriteLine(n - even[e1] - odd[o1]);
        }
    }
}