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# (.NET Core 3.1.201) (judge verdict: Accepted)

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

class Program
{
    static void Main(string[] args)
    {
        var n = int.Parse(ReadLine());
        var v = ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();

        var evenV = v.Where((v, i) => i % 2 == 0).GroupBy(x => x).Select(g => (v: g.Key, c: g.Count())).OrderByDescending(x => x.c).ToArray();
        var oddV = v.Where((v, i) => i % 2 == 1).GroupBy(x => x).Select(g => (v: g.Key, c: g.Count())).OrderByDescending(x => x.c).ToArray();

        var ans = 0;

        if (evenV[0].v != oddV[0].v)
        {
            ans = n - evenV[0].c - oddV[0].c;
        }
        else
        {
            if(1 < evenV.Length && 1 < oddV.Length)
            {
                var a = n - evenV[0].c - oddV[1].c;
                var b = n - evenV[1].c - oddV[0].c;
                ans = Math.Min(a, b);
            }
            else if(1 < evenV.Length)
            {
                ans = n - evenV[1].c - oddV[0].c;
            }
            else if(1 < oddV.Length)
            {
                ans = n - evenV[0].c - oddV[1].c;
            }
            else
            {
                ans = n / 2;
            }
        }

        WriteLine(ans);
    }
}