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.Linq;
using System.Collections.Generic;
namespace aoj
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] A = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
            Dictionary<int, int> dic = new Dictionary<int, int>(n / 2);
            Dictionary<int, int> evendic = new Dictionary<int, int>(n / 2);
            Dictionary<int, int> odddic = new Dictionary<int, int>(n / 2);
            for (int i = 0; i < n; i++)
            {
                if (dic.ContainsKey(A[i])) dic[A[i]] += 1;
                else dic[A[i]] = 1;
                if (i % 2 == 0)
                {
                    if (evendic.ContainsKey(A[i])) evendic[A[i]] += 1;
                    else evendic[A[i]] = 1;
                }
                else
                {
                    if (odddic.ContainsKey(A[i])) odddic[A[i]] += 1;
                    else odddic[A[i]] = 1;
                }

            }
            if (dic.Values.Count == 1) Console.WriteLine(n / 2);
            else
            {
                int[] even = new int[evendic.Values.Count];
                int[] odd = new int[odddic.Values.Count];
                evendic.Values.CopyTo(even, 0);
                odddic.Values.CopyTo(odd, 0);

                int evenMax = even.Max();
                int evenSum = even.Sum();
                int oddMax = odd.Max();
                int oddSum = odd.Sum();
                Console.WriteLine(evenSum - evenMax + oddSum - oddMax);
            }
        }
    }
}