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 <bits/stdc++.h>
using namespace std;
 
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	int n; cin >> n;
	map<int, int> mp1, mp2;
	for(int i = 0; i < n; i++) {
		int s; cin >> s;
		if(i % 2 == 0) mp1[s]++;
		else mp2[s]++;
	}
	int a = 0, b = 0;
	int cnt1 = 0, cnt2 = 0;
	for(int i = 1; i <= 100000; i++){
		int c = cnt1, d = a;
		if(mp1[i] > cnt1) {
				cnt1 = mp1[i];
				a = i;
		}
		if(mp2[i] > cnt2) {
			if(i == a) {
				if(mp2[i] > cnt1){
					cnt2 = mp2[i];
					b = i;
					cnt1 = c;
					a = d;
				}
			}
			else{
				cnt2 = mp2[i];
				b = i;
			}
		}	
	}
	cout << n - cnt1 - cnt2 << endl;
	return 0;                                              
}