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: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>

typedef struct map{
	int n;
	int count;
	struct map *next;
}map;

map *search(int n, map *top){
	if(top == NULL)return NULL;
	if(top->n == n)return top;
	return search(n, top->next);
}

void *add(int n, map *top){
	map *res = search(n, top);
	if(res)res->count++;
	else{
		res = malloc(sizeof(map));
		res->next = top->next;
		res->n = n;
		res->count = 1;
		top->next = res;
	}
}

int max(map *top){
	if(top == NULL)return 0;
	int ret = max(top->next);
	if(top->count > ret)ret = top->count;
	return ret;
}

void printmap(map *top){
	if(top == NULL)return;
	printmap(top->next);
}

int main(void){
	map a = {.n = 0, .next = NULL}, b = {.n = 0, .next = NULL};
	int n, in;
	scanf("%d", &n);
	for(int i = 0; i < n; i++){
		scanf("%d", &in);
		if(i % 2)add(in, &a);
		else add(in, &b);
	}
	printf("%d\n", n - max(&a) - max(&b));
	return 0;
}