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 <bits/stdc++.h>
using namespace std;
int main() {
    int n;
    cin >> n;
    map<int, int> odds;
    map<int, int> evens;
    for(int i = 0; i < n; i++) {
        int v;
        cin >> v;
        if(i % 2 == 0) {
            evens[v]++;
        } else {
            odds[v]++;
        }
    }

    vector<pair<int, int>> odds_freq(0);
    vector<pair<int, int>> evens_freq(0);
    for(pair<int, int> kv : odds) {
        odds_freq.push_back({kv.second, kv.first});
    }
    for(pair<int, int> kv : evens) {
        evens_freq.push_back({kv.second, kv.first});
    }
    sort(odds_freq.begin(), odds_freq.end(), greater<pair<int, int>>());
    sort(evens_freq.begin(), evens_freq.end(), greater<pair<int, int>>());

    int ans = 0;
    if(odds_freq.at(0).second == evens_freq.at(0).second) {
        int ans1 = 0;
        for(int i = 1; i < odds_freq.size(); i++) {
            ans1 += odds_freq.at(i).first;
        }
        for(int i = 0; i < evens_freq.size(); i++) {
            if(i == 1) {
                continue;
            }
            ans1 += evens_freq.at(i).first;
        }
        int ans2 = 0;
        for(int i = 0; i < odds_freq.size(); i++) {
            if(i == 1) {
                continue;
            }
            ans2 += odds_freq.at(i).first;
        }
        for(int i = 1; i < evens_freq.size(); i++) {
            ans2 += evens_freq.at(i).first;
        }
        ans = min(ans1, ans2);
    } else {
        for(int i = 1; i < odds_freq.size(); i++) {
            ans += odds_freq.at(i).first;
        }
        for(int i = 1; i < evens_freq.size(); i++) {
            ans += evens_freq.at(i).first;
        }
    }

    cout << ans << endl;

    return 0;
}