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 <vector>
#include <algorithm>
#include <map>
#include <unordered_map>
using namespace std;

vector<pair<int, int>> mapvector(unordered_map<int, int> map){
    vector<pair<int, int>> pairs;
    for (pair<int, int> p : map){
        pairs.push_back(make_pair(p.second, p.first));
    }
    sort(pairs.begin(), pairs.end(), greater<pair<int, int>>());
    return pairs;
}

int main(){
    int n;
    cin >> n;
    vector<int> even(n/2);
    vector<int> odd(n/2);
    for(int i = 0; i < n; i++)
    {
        if (i%2 == 0) {
            cin >> even.at(i/2);
        }
        else
        {
            cin >> odd.at(i/2);
        }
    }

    unordered_map<int, int> evenmap, oddmap;
    for (int i : even){
        if (evenmap.find(i) != evenmap.end()) {
            evenmap[i]++;
        }
        else
        {
            evenmap[i] = 1;
        }
    }
    for (int i : odd){
        if (oddmap.find(i) != oddmap.end()) {
            oddmap[i]++;
        }
        else
        {
            oddmap[i] = 1;
        }
    }

    vector<pair<int, int>> evenfreq = mapvector(evenmap);
    vector<pair<int, int>> oddfreq = mapvector(oddmap);
    pair<int, int> e1 = evenfreq.at(0);
    pair<int, int> o1 = oddfreq.at(0);
    pair<int, int> e2, o2;
    if (evenfreq.size() > 1) {
        e2 = evenfreq.at(1);
    }
    else
    {
        e2 = make_pair(0, -1);
    }
    if (oddfreq.size() > 1) {
        o2 = oddfreq.at(1);
    }
    else
    {
        o2 = make_pair(0, -1);
    }

    int ans;
    if (e1.second != o1.second) {
        ans = n - e1.first - o1.first;
    }
    else
    {
        ans = min(n-e1.first-o2.first, n-e2.first-o1.first);
    }
    
    cout << ans << endl;
}