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;

namespace Myatcoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            int[] A = Console.ReadLine().Split().Select(x => int.Parse(x)).ToArray();
            Dictionary<int, int> Even = new Dictionary<int, int>(n / 2);
            Dictionary<int, int> Odd = new Dictionary<int, int>(n / 2);
            for (int i = 0; i < n / 2; i++) {
                if (Even.ContainsKey(A[i * 2]) && !Odd.ContainsKey(A[i * 2])) Even[A[i * 2]]++;
                else Even[A[i * 2]] = 1;
                if (Odd.ContainsKey(A[i * 2 + 1]) && !Even.ContainsKey(A[i * 2 + 1])) Odd[A[i * 2 + 1]]++;
                else Odd[A[i * 2 + 1]] = 1;
            }
            int count = 0;
            for (int i = 1; i < n; i++) {
                if (A[0] == A[i]) count++;
                else break;
            }
            if (count != n - 1) Console.WriteLine(n - Even.Values.Max() - Odd.Values.Max());
            else Console.WriteLine(n / 2);
        }
    }
}