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;
using System.Collections.Generic;

class Program
{
    public static void Main()
    {
        int N = int.Parse(Console.ReadLine());
        string[] d = Console.ReadLine().Split(' ');
        int[] a = new int[N];
        for (int i = 0; i < N; i++)
            a[i] = int.Parse(d[i]);

        int evensum = 0, oddsum = 0;
        Dictionary<int, int> EvenDic = new Dictionary<int, int>();
        Dictionary<int, int> OddDic = new Dictionary<int, int>();
        for (int i = 0; i < N; i += 2)
        {
            if (EvenDic.ContainsKey(a[i]))
                EvenDic[a[i]]++;
            else
                EvenDic.Add(a[i], 1);
            evensum++;
        }
        for (int i = 1; i < N; i += 2)
        {
            if (OddDic.ContainsKey(a[i]))
                OddDic[a[i]]++;
            else
                OddDic.Add(a[i], 1);
            oddsum++;
        }

        List<KeyValuePair<int, int>> EvenList = new List<KeyValuePair<int, int>>() { Capacity = EvenDic.Count };
        List<KeyValuePair<int, int>> OddList = new List<KeyValuePair<int, int>>() { Capacity = OddDic.Count };

        foreach (var i in EvenDic)
            EvenList.Add(i);
        foreach (var i in OddDic)
            OddList.Add(i);

        EvenList.Sort((x, y) => x.Value - y.Value);
        OddList.Sort((x, y) => x.Value - y.Value);

        int s = 0;
        if(EvenList[EvenList.Count - 1].Key == OddList[OddList.Count - 1].Key)
        {
            if ((evensum - EvenList[EvenList.Count - 1].Value) < (oddsum - OddList[OddList.Count - 1].Key))
            {
                s += evensum - EvenList[EvenList.Count - 1].Value;
                if (OddList.Count > 1)
                    s += oddsum - OddList[OddList.Count - 2].Value;
                else
                    s += oddsum;
            }
            else
            {
                if (EvenList.Count > 1)
                    s += evensum - EvenList[EvenList.Count - 2].Value;
                else
                    s += evensum;
                s += oddsum - OddList[OddList.Count - 1].Value;
            }
        }
        else
        {
            s += evensum - EvenList[EvenList.Count - 1].Value;
            s += oddsum - OddList[OddList.Count - 1].Value;
        }
        Console.WriteLine(s);
    }
}