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>
#define LL long long
#define mp make_pair
#define pb push_back
#define VI vector<int>
#define pii pair<int,int>
#define INF 0x3f3f3f3f
using namespace std;
const int MAXN = 1e5;
int A[MAXN+10], F[2][MAXN+10];
int n;
int main(){
	scanf("%d", &n);
	for(int i = 0; i < n; i++){
		scanf("%d", &A[i]);
		F[i%2][A[i]]++;
	}
	int ans = INF;
	for(int i = 0; i < n - 1; i++){
		if(A[i] == A[i+1]) continue;
		ans = min(ans, n - F[i%2][A[i]] - F[(i+1)%2][A[i+1]]);
	}
	if(ans == INF) ans = n/2;
	printf("%d\n", ans);
	return 0;
}