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<cstdio>
#include<algorithm>
using namespace std;
int n,v[100005],a[100005],b[100005];
int main(){
	scanf("%d",&n);for(int i=1;i<=n;++i) scanf("%d",&v[i]);
	for(int i=2;i<=n;i+=2) a[v[i]]++,b[v[i-1]]++;
	int c1=0,c2=0,k1,k2;
	for(int i=1;i<=100000;++i) {if(a[i]>c1) c1=a[i],k1=i;if(b[i]>c2) c2=b[i],k2=i;}
	if(k1==k2) {
		int c3=0,c4=0;
		for(int i=1;i<=100000;++i) {if(a[i]>c3&&k1!=i) c3=a[i];if(b[i]>c4&&k1!=i) c4=b[i];}
		printf("%d\n",min(n-c1-c3,n-c2-c4));
		return 0;
	}
	printf("%d\n",n-c1-c2);
	return 0;
}