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;
using System.Linq;


public class C{
	
	public static void Main(){
	
		int n = Int32.Parse( Console.ReadLine() );		
		Dictionary<int, int> even = new Dictionary<int, int>(n);
		Dictionary<int, int> odd = new Dictionary<int, int>(n);
		string[] args = Console.ReadLine().Split(' ');
		for(int i = 0; i < n; i++){
			int v = Int32.Parse(args[i]);
			if((i % 2) == 0){
				if(even.ContainsKey(v)){
					even[v]++;
				}else{
					even.Add(v,1);
				}
			}else{
				if(odd.ContainsKey(v)){
					odd[v]++;
				}else{
					odd.Add(v,1);
				}
			}			
		}
		
		int evenMax1 = even.OrderBy(x => x.Value).Last().Key;
		int numEvenMax1 = even[evenMax1];
		even.Remove(evenMax1);
		int evenMax2 = 0, numEvenMax2 = 0;
		if(even.Count > 0){
			evenMax2 = even.OrderBy(x => x.Value).Last().Key;
			numEvenMax2 = even[evenMax2];
		}
		
		int oddMax1 = odd.OrderBy(x => x.Value).Last().Key;
		int numOddMax1 = odd[oddMax1];
		odd.Remove(oddMax1);
		int oddMax2 = 0, numOddMax2 = 0;
		if(odd.Count > 0){
			oddMax2 = odd.OrderBy(x => x.Value).Last().Key;
			numOddMax2 = odd[oddMax2];
		}
		
		if( evenMax1 != oddMax1 ){
			Console.WriteLine(n - (numEvenMax1 + numOddMax1));
			
		}else if( numEvenMax2 == 0 && numOddMax2 == 0 ){
			Console.WriteLine(n - 
				Math.Max(numEvenMax1, numOddMax1));
		
		}else if( numEvenMax2 == 0 ){
			Console.WriteLine(n - 
				(numEvenMax1 + numOddMax2));
			
		}else if( numOddMax2 == 0 ){
			Console.WriteLine(n - 
				(numEvenMax1 + numOddMax2));
			
		}else{
			Console.WriteLine( n - 
				Math.Max(
					numEvenMax1 + numOddMax2, 
					numEvenMax2 + numOddMax1
				)
			);	
		}
		
	}
	
}