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: Wrong Answer)

#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
using ll = long long;

int main() {
	int n;
	cin >> n;
	int a[n], odd[100010] = {}, even[100010] = {}, oddc[100010] = {}, evenc[100010] = {};
	for (int i = 1;i <= n;i++) {
		cin >> a[i];
		if (i % 2 == 0)even[a[i]]++;
		else odd[a[i]]++;
		if (i % 2 == 0)evenc[a[i]]++;
		else oddc[a[i]]++;
	}
	sort(evenc, evenc + 100010);
	sort(oddc, oddc + 100010);
	int me1 = 0, me2 = 0, mo1 = 0, mo2 = 0;
	for (int i = 0;i <= 100000;i++) {
		if (odd[i] == oddc[100009])mo1 = i;
		else if (odd[i] == oddc[100008])mo2 = i;
		if (even[i] == evenc[100009])me1 = i;
		else if (even[i] == evenc[100009])me2 = i;
	}
	if (mo1 != me1) {
		cout << n  - oddc[100009] - evenc[100009] << endl;
	}
	else if (mo2 > me2) {
		cout << n  - oddc[100008] - evenc[100009] << endl;
	}
	else cout << n  - oddc[100009] - evenc[100008] << endl;
}