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 (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main(void) {
	int n;
	int v[100000];
	int v1[100000] = {0};
	int pv1 = 0;
	int pv2 = 0;
	int pv2_2 = 0;
	int pv1_2 = 0;
	int v2[100000] = {0};
	
	scanf("%d", &n);
	
	for (int i=0; i<n; i++) {
		scanf("%d", &v[i]);
		if (i % 2 == 0) {
			v2[v[i]]++;
			if (v2[pv2] < v2[v[i]]) {
				pv2_2 = pv2;
				pv2 = v[i];
			} else {
				if (v2[pv2_2] < v2[v[i]] && v[i] != pv2)
					pv2_2 = v[i];
			}
		} else {
			v1[v[i]]++;
			if (v1[pv1] < v1[v[i]]) {
				pv1_2 = pv1;
				pv1 = v[i];
			} else {
				if (v1[pv1_2] < v1[v[i]] && v[i] != pv1)
					pv1_2 = v[i];
			}
		}
	}
	
	if (pv1 == pv2) {
		if (v1[pv1_2] > v2[pv2_2])
			pv1 = pv1_2;
		else
			pv2 = pv2_2;
	}
	
	int cnt = 0;
	for (int i=0; i<n; i++) {
		if (i % 2 == 0) {
			if (v[i] != pv2)cnt++;
		} else {
			if (v[i] != pv1)cnt++;
		}
	}
	
	printf("%d", cnt);
	
	return 0;
}