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;

    vector<int> V(N);
    for (int i = 0; i < N; i++) {
        cin >> V[i];
    }

    vector<int> A1(100100);
    vector<int> A2(100100);
    for (int i = 0; i < 100100; i++) {
        A1[i] = 0;
        A2[i] = 0;
    }
    for (int i = 0; i < N; i++) {
        if (i % 2 == 0) {
            A1[V[i]]++;
        }
        else {
            A2[V[i]]++;
        }
    }

    int V11 = 0;
    int V12 = 0;
    int V21 = 0;
    int V22 = 0;
    for (int i = 0; i < 100100; i++) {
        if (V11 < A1[i]) {
            V11 = A1[i];
            V12 = i + 1;
        }
        if (V21 < A2[i]) {
            V21 = A2[i];
            V22 = i + 1;
        }
    }

    sort(A1.begin(), A1.end());
    reverse(A1.begin(), A1.end());
    sort(A2.begin(), A2.end());
    reverse(A2.begin(), A2.end());

    if (V12 == V22) {
        cout << min((N / 2 - A1[0]) + (N / 2 - A2[1]), (N / 2 - A1[1]) + (N / 2 - A2[0])) << endl;
    }
    else {
        cout << (N / 2 - A1[0]) + (N / 2 - A2[0]) << endl;
    }
}