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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
class Program
{
	static void Main(string[] args)
	{
		int N = int.Parse(Console.ReadLine());
		int[]A = new int[N];
		int[]A2 = new int[N];
		string[] str = Console.ReadLine().Split();
		int[]B = new int[100001];
		int[]B2 = new int[100001];
		int[]C = new int[100001];
		int[]C2 = new int[100001];
		int[]D = new int[100001];
		int[]D2 = new int[100001];
		for(var i=0;i<N/2;i++){
			A[i] = int.Parse(str[i*2]);
			B[A[i]] += 1;
			A2[i] = int.Parse(str[i*2+1]);
			B2[A2[i]] += 1;
		}
		long ans = 0;
		Array.Sort(B, (x,y) => y - x);
		Array.Sort(B2, (x,y) => y - x);
		ans += N/2 - B[0];
		ans += N/2 - B2[0];
		for(var i=0;i<N/2;i++){
			C[A[i]] += 1;
			C2[A2[i]] += 1;
		}
		long at = -1;
		long ac = 0;
		long bt = -1;
		long bc = 0;
		for(var i=0;i<100001;i++){
			if(C[i] == B[0]){
				at = i;
				ac += 1;
			}
			if(C2[i] == B2[0]){
				bt = i;
				bc += 1;
			}
		}
		if(ac == 1 && bc == 1 && at == bt){
			ans = Math.Min(N/2 - B[0] + N/2 - B[1],N/2 - B2[0] + N/2 - B2[1]);
		}
		Console.WriteLine(ans);
	}
}