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 ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            //入力
            var n = int.Parse(Console.ReadLine());
            var a = Console.ReadLine();

            var arr = a.Split(' ');
            var ans = 0;
            var count = 0;
            var a1 = new Dictionary<int, int>();
            var a2 = new Dictionary<int, int>();

            for (int i = 0; i < n-1; i++)
            {
                var s = arr[i];

                if (count % 2 == 0)
                {
                    if (a1.ContainsKey(int.Parse(s)))
                    {
                        a1[int.Parse(s)] += 1;
                    }
                    else
                    {
                        a1.Add(int.Parse(s), 1);
                    }
                }
                else
                {
                    if (a2.ContainsKey(int.Parse(s)))
                    {
                        a2[int.Parse(s)] += 1;
                    }
                    else
                    {
                        a2.Add(int.Parse(s), 1);
                    }
                }
                count++;

            }
            if (a1.Count == 1 & a2.Count ==1)
            {
                if (a1.First().Key == a2.First().Key)
                {
                    ans = a1.First().Value;
                }
            }
            if (a1.Count > 1)
            {
                var a11 = a1.OrderBy(i => i.Value);
                ans += a11.Sum(i => i.Value) - a11.Last().Value;
                
            }
            if (a2.Count > 1)
            {
                var a22 = a1.OrderBy(i => i.Value);
                ans += a22.Sum(i => i.Value) - a22.Last().Value;
  
            }
            Console.WriteLine("{0}", ans);
            Console.ReadKey();
        }
    }
}