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<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<map>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

string yn(bool f){return f?"Yes":"No";}
string YN(bool f){return f?"YES":"NO";}



signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout<<fixed<<setprecision(10);
	
	int n;
	int ans = INF;
	int max11 = 0, max11i = -1;
	int max12 = 0, max12i = -1;
	int max21 = 0, max21i = -1;
	int max22 = 0, max22i = -1;
	
	vector<int> v;
	map<int,int> mp1, mp2;
	
	cin>>n;
	
	v.resize(n);
	
	for(int i = 0; i < n; i++){
		cin>>v[i];
		
		if(i%2) {
			mp1[v[i]]++;
		} else {
			mp2[v[i]]++;
		}
	}
	
	for(pair<int,int> p : mp1){
		if(max11 <= p.second) {
			max12 = max11;
			max12i = max11i;
			
			max11 = p.second;
			max11i = p.first;
			
			
		} else if(max12 <= p.second) {
			max12 = p.second;
			max12i = p.first;
			
		}
	}
	
	for(pair<int,int> p : mp2){
		if(max21 <= p.second) {
			max22 = max21;
			max22i = max21i;
			
			max21 = p.second;
			max21i = p.first;
		} else if(max22 <= p.second) {
			max22 = p.second;
			max22i = p.first;
			
		}
	}
	
	// n /= 2;
	
	ans = n;

	// cout<<max11i<<" <>  "<<max21i<<endl;
	// cout<<max11<<" <>  "<<max21<<endl;cout<<endl;
	if(max11i != max21i) {
		ans = min(ans, n - max11 - max21);
	}
	// cout<<max12i<<" <>  "<<max21i<<endl;
	// cout<<max12<<" <>  "<<max21<<endl;cout<<endl;
	if(max12i != max21i) {
		
		ans = min(ans, n - max12 - max21);
	}
	
	// cout<<max11i<<" <>  "<<max22i<<endl;
	if(max11i != max22i) {
		ans = min(ans, n - max11 - max22);
	}
	
	// cout<<max12i<<" <>  "<<max22i<<endl;
	if(max12i != max22i) {
		ans = min(ans, n - max12 - max22);
	}
	
	cout<<ans<<endl;
	return 0;
}