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 n;
int k[100010]; // 奇数
int g[100010]; // 偶数

int kn, gn; // 奇数・偶数の頻出数字の頻出数
int main()
{
	int kmx1, kmx2;
	int gmx1, gmx2;
	int tmp;
	
	kmx1 = kmx2 = gmx1 = gmx2 = -1;
	cin >> n;
	for( int i = 0; i < n/2; i++ ) {
		cin >> tmp;
		k[tmp]++;
		if( kn < k[tmp] ) {
			if( kmx1 != tmp ) {
				kmx2 = kmx1;
				kmx1 = tmp;
			}
			kn = k[tmp];
		} else if( k[kmx2] < k[tmp] ) {
			kmx2 = tmp;
		}
		cin >> tmp;
		g[tmp]++;
		if( gn < g[tmp] ) {
			if( gmx1 != tmp ) {
				gmx2 = gmx1;
				gmx1 = tmp;
			}
			gn = g[tmp];
		} else if( g[gmx2] < g[tmp] ) {
			gmx2 = tmp;
		}
	}
	/*
	cout << "kmx:" << kmx1 << " " << kmx2 << endl;
	cout << "gmx:" << gmx1 << " " << gmx2 << endl;
	cout << "xn:" << kn << " " << gn << endl;
	*/
	if( kmx1 == gmx1 ) {
		if( kn < gn ) {
			kmx1 = kmx2;
			if( kmx1 == -1 ) {
				kn = 0;
			} else {
				kn = k[kmx1];
			}
		} else {
			gmx1 = gmx2;
			if( gmx1 == -1 ) {
				gn = 0;
			} else {
				gn = g[kmx1];
			}
		}
	}
	cout << (n - (kn+gn)) << endl;
}