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;

    class Program
    {
        static void Main(string[] args)
        {
            var halfCount = int.Parse(Console.ReadLine())/2;
            var input = Console.ReadLine().Split(' ').Select(x=>int.Parse(x));
            var oddList = new List<int>();
            var evenList = new List<int>();
            foreach (var num in input.Select((x, i) => new { i, x }))
            {
                if(num.i%2==0)
                {
                    evenList.Add(num.x);
                    continue;
                }
                oddList.Add(num.x);
            }
            var oddCount = oddList.GroupBy(x => x).Select(x=>x.Count()).Max();
            var evenCount = evenList.GroupBy(x => x).Select(x=>x.Count()).Max();

            //exceptional
            if(oddList.SequenceEqual(evenList))
            {
                Console.WriteLine(halfCount);
                return;
            }
            var lessCount = oddCount > evenCount ? evenCount : oddCount;
            Console.WriteLine(halfCount-lessCount);
        }
    }