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: Runtime Error)

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

class Program
{
    static void Main(string[] args)
    {
        int n = ReadLineParseInt();
        string[] s = ReadLine().Split(' ');
        int[] even = new int[100001];
        int[] odd = new int[10001];
        for(int i = 0; i < n; i += 2)
            even[int.Parse(s[i])]++;

        for (int i = 1; i < n; i += 2)
            odd[int.Parse(s[i])]++;

        int evenMax = 0;
        int evenMaxIndex = 0;
        int evenSubMax = 0;
        int evenSubMaxIndex = 0;
        for(int i = 0; i < even.Length; i++)
        {
            if(even[i] >= evenMax)
            {
                evenSubMax = evenMax;
                evenSubMaxIndex = evenMaxIndex;
                evenMax = even[i];
                evenMaxIndex = i;
            }
        }

        int oddMax = 0;
        int oddMaxIndex = 0;
        int oddSubMax = 0;
        int oddSubMaxIndex = 0;
        for (int i = 0; i < odd.Length; i++)
        {   
            if (odd[i] >= oddMax)
            {
                oddSubMax = oddMax;
                oddSubMaxIndex = oddMaxIndex;
                oddMax = odd[i];
                oddMaxIndex = i;
            }
        }
        if (evenMaxIndex == oddMaxIndex)
            WriteLine(n - Max(evenMax + oddSubMax, evenSubMax + oddMax));
        else
            WriteLine(n - evenMax - oddMax);
    }
    static int ReadLineParseInt() => int.Parse(ReadLine());
}