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.Diagnostics;
using System.IO;
using System.Text;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args) {
#if DEBUG
        MyDebugger.Test(process, "../TextFile1.txt");
        //MyDebugger.Test(process, "../TextFile2.txt");
        //MyDebugger.MakeTestCase("../TextFile2.txt");
#else
        object ret = process(new StreamReader(Console.OpenStandardInput()));
        Console.WriteLine(ret);
#endif
    }

    static object process(TextReader input) {
        var n = int.Parse(input.ReadLine());
        var vv = ToIntArray(input.ReadLine(), n);

        var dic1 = new Dictionary<int, Num>();
        var dic2 = new Dictionary<int, Num>();

        for(int i=1; i<=100000; i++) {
            dic1.Add(i, new Num() { v = i });
            dic2.Add(i, new Num() { v = i });
        }

        for(int i=0; i<n; i++) {
            Dictionary<int, Num> dic;
            dic = (i % 2 == 0) ? dic1 : dic2;
            dic[vv[i]].c++;
        }

        var ary1 = dic1.Values.ToList();
        var ary2 = dic2.Values.ToList();

        ary1.Sort((x, y) => y.c.CompareTo(x.c));
        ary2.Sort((x, y) => y.c.CompareTo(x.c));

        var r1 = ary1[0];
        var r2 = ary2[0];
        var c = int.MinValue;
        
        Action<Num, Num> Count = (x, y) => {
            if (x.v == y.v) return;

            var z = x.c + y.c;
            if(z > c) {
                c = z;
                r1 = x;
                r2 = y;
            }
        };

        Count(ary1[0], ary2[0]);
        Count(ary1[0], ary2[1]);
        Count(ary1[1], ary2[0]);
        Count(ary1[1], ary2[1]);

        return n - r1.c - r2.c;
    }

    class Num
    {
        public int v;
        public int c;
    }

    static int[] ToIntArray(string strs, int n) {
        var ret = new int[n];
        var spl = strs.Split(' ');
        for (int i = 0; i < n; i++)
            ret[i] = int.Parse(spl[i]);
        return ret;
    }
}