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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <map>
#include <algorithm>

using namespace std;

int main(){

    int n;

    cin >> n;
    map<int,int> odd_map;
    map<int,int> even_map;
    int odd_max = 0;
    int odd_2nd = 0;
    int odd_num;
    int even_max = 0;
    int even_2nd = 0;
    int even_num;

    for(int i = 1; i <= n; i++){
        int tmp;
        cin >> tmp;
        
        if(i % 2 == 1){
            odd_map[tmp]++;
            if(odd_max <= odd_map[tmp]){
                if(odd_num != tmp) odd_2nd = odd_max;
                odd_num = tmp;
                odd_max = odd_map[tmp];
            }else{
                if(odd_2nd < odd_map[tmp]){
                    odd_2nd = odd_map[tmp];
                }
            }
        }else{
            even_map[tmp]++;
            if(even_max <= even_map[tmp]){
                if(even_num != tmp) even_2nd = even_max;
                even_num = tmp;
                even_max = even_map[tmp];
            }else{
                if(even_2nd < even_map[tmp]){
                    even_2nd = even_map[tmp];
                }
            }
        }
    }

    if(odd_num != even_num){
        cout << n - odd_max - even_max << endl;
    }else{
        if(odd_2nd < even_2nd){
            cout << n - odd_max - even_2nd << endl;
        }else{
            cout << n - odd_2nd - even_max << endl;
        }
    }

    return 0;
}