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.Collections.Generic;
using System.Linq;

namespace c
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] v = Console.ReadLine().Split().Select(s => int.Parse(s)).ToArray();
            var dict1 = new Dictionary<int, int>();
            var dict2 = new Dictionary<int, int>();
            for(int i = 0; i < n; i++){
                int k = v[i];
                if(i%2 == 0)
                {
                    if(dict1.ContainsKey(k))
                    {
                        dict1[k]++;
                    }
                    else
                    {
                        dict1.Add(k, 1);
                    }
                }
                else
                {
                    if (dict2.ContainsKey(k))
                    {
                        dict2[k]++;
                    }
                    else
                    {
                        dict2.Add(k, 1);
                    }
                }
            }
            var d1 = dict1.OrderByDescending((x) => x.Value);
            var d2 = dict2.OrderByDescending((x) => x.Value);
            var dd1 = d1.ToArray();
            var dd2 = d2.ToArray();

            int res = 0;
            if (dd1[0].Key == dd2[0].Key)
            {
                int c1 = 0, c2 = 0;
                if (dd2.Count() > 1)
                {
                    c1 = dd1[0].Value + dd2[1].Value;
                }
                else
                {
                    c1 = dd1[0].Value;
                }
                if (dd1.Count() > 1)
                {
                    c2 = dd2[0].Value + dd1[1].Value;
                }
                else
                {
                    c2 = dd2[0].Value;
                }
                if (c1 > c2)
                {
                    res = n - c1;
                }
                else
                {
                    res = n - c2;
                }
            }
            else
            {
                res = n - (dd1[0].Value + dd2[0].Value);
            }
            Console.WriteLine(res);
        }
    }
}