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;
using static System.Console;
using static System.Convert;
using static System.Math;

class Program
{
    static void Main(string[] args)
    {
        var num = ToInt32(ReadLine());
        var nums = Array.ConvertAll(ReadLine().Split(' '), int.Parse);
        var dic = new Dictionary<int, int>();
        var dic2 = new Dictionary<int, int>();
        var last = nums[0];
        var isSame = true;
        for(var i = 0; i < num; i++)
        {
            if (i % 2 == 0)
            {
                if (dic.ContainsKey(nums[i])) dic[nums[i]]++;
                else dic[nums[i]] = 1;
            }else
            {
                if (dic2.ContainsKey(nums[i])) dic2[nums[i]]++;
                else dic2[nums[i]] = 1;
            }
            if (last != nums[i]) isSame = false;
        }
        if (isSame) { WriteLine(num / 2);return; }
        var max1 = dic.Values.Max();
        var maxKey1 = dic.First(d => d.Value == max1).Key;
        var max2 = dic2.Values.Max();
        var maxKey2 = dic2.First(d => d.Value == max2).Key;
        var result1 = 0;
        for(var i = 0; i < num; i++)
        {
            if (i % 2 == 0)
            {
                if (nums[i] == maxKey1) result1++;
            }
            else
            {
                if (nums[i] ==maxKey2) result1++;
            }
        }
        WriteLine(num - result1);
    }
}