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.Diagnostics.CodeAnalysis;
using System.Linq;

class Program {
    static void Main(string[] args) {
        int n;
        Input(out n);
        int[] v;
        InputArray(out v);
        int[] r1 = new int[100000];
        int[] r2 = new int[100000];
        for(int i = 0; i < n; i += 2) {
            r1[v[i] - 1]++;
        }
        for(int i = 1; i < n; i += 2) {
            r2[v[i] - 1]++;
        }
        if(Array.IndexOf(r1, r1.Max()) == Array.IndexOf(r2, r2.Max()) && Array.IndexOf(r1, r1.Max()) == Array.LastIndexOf(r1, r1.Max()) && Array.IndexOf(r2, r2.Max()) == Array.LastIndexOf(r2, r2.Max())) {
            int[] sorted_r1 = r2.Clone() as int[];
            int[] sorted_r2 = r2.Clone() as int[];
            if(sorted_r1[0] + sorted_r2[1] > sorted_r1[1] + sorted_r2[0]) {
                Console.WriteLine((n / 2 - sorted_r1[0]) + (n / 2 - sorted_r2[1]));
            } else {
                Console.WriteLine((n / 2 - sorted_r1[1]) + (n / 2 - sorted_r2[0]));
            }
        } else {
            Console.WriteLine((n / 2 - r1.Max()) + (n / 2 - r2.Max()));
        }
    }
    static T ChangeT<T>(string s) => (T)Convert.ChangeType(s, typeof(T));
    static void Input<A>(out A a) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
    }
    static void Input<A, B>(out A a, out B b) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
    }
    static void Input<A, B, C>(out A a, out B b, out C c) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
    }
    static void Input<A, B, C, D>(out A a, out B b, out C c, out D d) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
        d = ChangeT<D>(words[3]);
    }
    static void Input<A, B, C, D, E>(out A a, out B b, out C c, out D d, out E e) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
        d = ChangeT<D>(words[3]);
        e = ChangeT<E>(words[4]);
    }
    static void Input<A, B, C, D, E, F>(out A a, out B b, out C c, out D d, out E e, out F f) {
        var words = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries);
        a = ChangeT<A>(words[0]);
        b = ChangeT<B>(words[1]);
        c = ChangeT<C>(words[2]);
        d = ChangeT<D>(words[3]);
        e = ChangeT<E>(words[4]);
        f = ChangeT<F>(words[5]);
    }
    static void InputArray<T>(out T[] array) {
        array = Console.ReadLine().Split(new[] { ' ' }, options: StringSplitOptions.RemoveEmptyEntries).Select(s => ChangeT<T>(s)).ToArray();
    }
}