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;
 
static class MainClass {

  public static void Main (string[] args) {
    var N = ReadLineInt();
    var L = ReadLineLongList();

    var ans = 0;
    if(L.Distinct().Count() == 1){
      ans = N / 2;
      Console.WriteLine(ans);
      return;
    }
 
   	var test = N / 2 - L.Where((x, i) => i % 2 == 0).GroupBy(g => g).Select((x, i) => x.Count()).Max();

    var test2 = N / 2 - L.Where((x, i) => i % 2 == 1).GroupBy(g => g).Select((x, i) => x.Count()).Max();


    var even = L.Where((x, i) => i % 2 == 0).GroupBy(g => g).Select(g => new { n = g.Key, c = g.Count()}).OrderByDescending(x => x.c).First();

    var odd = L.Where((x, i) => i % 2 == 1).GroupBy(g => g).Select(g => new { n = g.Key, c = g.Count()}).OrderByDescending(x => x.c).First();

    if(even.n == odd.n){
       var second = L.Where((x, i) => i % 2 == 1).GroupBy(g => g).Select(g => new { n = g.Key, c = g.Count()}).OrderByDescending(x => x.c).ElementAt(1);
       ans = N / 2 - second.c  + test;
    }else{
      ans = test + test2;
    }

    /*test.ToList().ForEach(Console.WriteLine);
    test2.ToList().ForEach(Console.WriteLine);*/
    Console.WriteLine(ans);
  }

  static int ReadLineInt() {
    return int.Parse(Console.ReadLine());
  }
 static string ReadLineString() {
    return Console.ReadLine();
  }
  static IEnumerable<long> ReadLineLongList() {
    return Console.ReadLine().Split(' ').Select(long.Parse);
  }

}