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;

namespace AtCoder {
    class Program {

        static void Main(string[] args) {

            var n = int.Parse(Console.ReadLine());
            var v = Console.ReadLine().Split(' ').Select(e => int.Parse(e)).ToList();
            v.Sort();
            var result = 0;
            var expect = 0;
            var used = 0;
            for(int i = 0; i < v.Count; i++) {

                if(i % (n / 2) == 0) {

                    expect = v[i];
                    if(used == expect) {

                        expect = -1;
                    } else {

                        used = expect;
                    }
                }
                if (expect != v[i]) {

                    result++;
                }
            }

            Console.WriteLine(result);
        }
    }
}