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 static System.Console;
using System.Collections.Generic;
using System.Linq;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var n = InputNum();
            var a = InputNumList();

            var a_odd = a.Where((x, ix) => ix % 2 == 0).ToList();
            var a_evn = a.Where((x, ix) => ix % 2 == 1).ToList();

            int max_odd = 0;
            int maxNumOdd = -1;
            foreach (var item in a_odd)
            {
                int tmp = a_odd.Count(x => x == item);
                int oldo = max_odd;
                max_odd = Math.Max(tmp, max_odd);
                if (max_odd != oldo) maxNumOdd = item;
            }
            int max_evn = 0;
            int maxNumEvn = -1;
            foreach (var item in a_odd)
            {
                int tmp = a_evn.Count(x => x == item);
                int olde = max_evn;
                max_evn = Math.Max(tmp, max_evn);
                if (max_evn != olde) maxNumEvn = item;
            }

            int ans = 0;
            if (maxNumEvn != maxNumOdd)
            {
                while (a_odd.Remove(maxNumOdd)) { }
                while (a_evn.Remove(maxNumEvn)) { }
                ans = a_odd.Count + a_evn.Count();
            }
            else
            {
                if (max_odd > max_evn)
                {
                    while (a_odd.Remove(maxNumOdd)) { }
                    while (a_evn.Remove(maxNumEvn)) { }
                    int max_evn2 = 0;
                    int maxNumEvn2 = -1;
                    foreach (var item in a_odd)
                    {
                        int tmp = a_evn.Count(x => x == item);
                        int olde = max_evn2;
                        max_evn2 = Math.Max(tmp, max_evn2);
                        if (max_evn2 != olde) maxNumEvn2 = item;
                    }
                    ans = a_odd.Count + a_evn.Count - max_evn2 + max_evn;
                }
                else
                {
                    if (max_odd > max_evn)
                    {
                        while (a_odd.Remove(maxNumOdd)) { }
                        while (a_evn.Remove(maxNumEvn)) { }
                        int max_odd2 = 0;
                        int maxNumOdd2 = -1;
                        foreach (var item in a_odd)
                        {
                            int tmp = a_odd.Count(x => x == item);
                            int oldo = max_odd2;
                            max_odd2 = Math.Max(tmp, max_odd2);
                            if (max_odd2 != oldo) maxNumOdd2 = item;
                        }
                        ans = a_odd.Count + a_evn.Count - max_odd2 + max_odd;
                    }
                }
            }
            WriteLine(ans);


        }

        static int InputNum()
        {
            return int.Parse(ReadLine());
        }
        static List<int> InputNumList()
        {
            return ReadLine().Split(' ').Select(int.Parse).ToList();
        }
    }
}