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 Scala (2.11.7) (judge verdict: Wrong Answer)

import java.io.{InputStream, OutputStream, PrintStream}
import java.util.Scanner

object Main {

  def main(args: Array[String]): Unit = {
    val solver = new Solver(System.in, System.out)
    solver.solve()
  }

  class Solver(in: InputStream, out: OutputStream) {
    lazy val input = new Scanner(in)

    lazy val output = new PrintStream(out)

    def solve(): Unit = {
      val n  = input.nextLine().toInt
      val vs = input.nextLine().split(" ").map(_.toInt)

      val (tops, bottoms) = vs.zipWithIndex.partition { case (v, i) => i % 2 == 0 }

      val results = for {
        (topVal, topCount) <- tops
          .map(_._1)
          .groupBy(identity)
          .map { case (v, vs) => (v, vs.size) }
          .toSeq
          .sortBy(_._2)
          .take(2)
        (bottomVal, bottomCount) <- bottoms
          .map(_._1)
          .groupBy(identity)
          .map { case (v, vs) => (v, vs.size) }
          .toSeq
          .sortBy(_._2)
          .take(2)
        if topVal != bottomVal
      } yield n - topCount - bottomCount

      if (results.isEmpty) {
        println(n/2)
      } else {
        println(results.min)
      }

    }

  }

}