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.Linq;
using System.Collections.Generic;

class M {static void Main(string[] _){
  
  Console.ReadLine();
  var A = Console.ReadLine().Split(' ');
  var B0 = A.Where( (a,i) => i % 2 == 0 );
  var B1 = A.Where( (a,i) => i % 2 == 1 );
  var C0 = B0.GroupBy(i=>i).OrderByDescending(i=>i.Count()).Select( i => new { k=int.Parse(i.Key) , v=i.Count()} ).ToList();
  var C1 = B1.GroupBy(i=>i).OrderByDescending(i=>i.Count()).Select( i => new { k=int.Parse(i.Key) , v=i.Count()} ).ToList();
  
  int D0k = C0[0].k;
  int D0v = C0[0].v;
  
  int D1k = C1[0].k;
  int D1v = C1[0].v;  
  
  if ( D0k == D1k ) {
    if ( D0v < D1v ) {
      if ( C0.Count == 1 ) {
        D0k += 1;
      } else {
	    D0k = C0[1].k;
      }
    } else {
      if ( C1.Count == 1 ) {
        D1k += 1;
      } else {
	    D1k = C1[1].k;
      }
    }
  }
  
  int E0 =B0.Where( i => int.Parse(i) != D0k ).Count();
  int E1 =B1.Where( i => int.Parse(i) != D1k ).Count();
  
  int result = E0 + E1;
  Console.Write(result);
  
}}