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: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;

namespace MyProgram{
    class AtCoder{
        static void Main(){
            var N = int.Parse(Console.ReadLine());
            var v = Console.ReadLine().Split(' ').Select(int.Parse).ToArray();
            var dict_odd = new Dictionary<int,int>();
            var dict_even = new Dictionary<int,int>();
            for(var i=0;i<N;i++){
                if(i%2==0){
                    if(!dict_odd.ContainsKey(v[i]))dict_odd[v[i]]=0;
                    dict_odd[v[i]]++;
                }else if(i%2==1){
                    if(!dict_even.ContainsKey(v[i]))dict_even[v[i]]=0;
                    dict_even[v[i]]++;
                }
            }
            var odd_list = new List<Arr>();
            var even_list = new List<Arr>();
            foreach(var key in dict_odd.Keys){
                var a = new Arr();
                a.key = key;
                a.value = dict_odd[key];
                odd_list.Add(a);
            }
            foreach(var key in dict_even.Keys){
                var a = new Arr();
                a.key = key;
                a.value = dict_even[key];
                even_list.Add(a);
            }
            odd_list.Sort(delegate(Arr a,Arr b){return b.value-a.value;});
            even_list.Sort(delegate(Arr a,Arr b){return b.value-a.value;});
            int result;
            if(odd_list[0].key != even_list[0].key){
                result = N - odd_list[0].value - even_list[0].value;
            }else if(N>4){
                result = Math.Min(N - odd_list[1].value - even_list[0].value,N - odd_list[0].value - even_list[1].value);
            }else{
                result = N/2;
            }

            System.Console.WriteLine(result);
        }

    }
    public class Arr{
        public int key;
        public int value;
    }
}