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.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC111C
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.ReadLine();
            var input = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            var ans = 0;

            if (input.Distinct().Count() == 1)
            {
                ans = input.Length / 2;
            }
            else
            {
                var input1 = input.Select((x, i) => new { x, i }).Where(x => x.i % 2 == 0).Select(x => x.x);
                var input2 = input.Select((x, i) => new { x, i }).Where(x => x.i % 2 == 1).Select(x => x.x);

                var group2 = input1.GroupBy(x => x).OrderBy(x => x.Count()).ToArray();
                var group1 = input2.GroupBy(x => x).OrderBy(x => x.Count()).ToArray();

                if (group1.First().Count() < group2.First().Count())
                {
                    var tmp = (IGrouping<int, int>[])group1.Clone();
                    group1 = (IGrouping<int, int>[])group2.Clone();
                    group2 = tmp;
                }

                var cnt = group1.Skip(1).Sum(x => x.Count());
                var max = group2.First(x => x.Key != group1.First().Key).Key;

                cnt += group2.Where(x => x.Key != max).Sum(x => x.Count());

                ans = cnt;
            }

            Console.WriteLine(ans);
        }
    }
}