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: Runtime Error)

object Main {
  import java.util.Scanner

  def readStrings(n: Int)(implicit sc: Scanner): Array[String] = Array.fill(n) { sc.next() }
  def readInts(n: Int)(implicit sc: Scanner): Array[Int] = Array.fill(n) { sc.nextInt() }
  def readLongs(n: Int)(implicit sc: Scanner): Array[Long] = Array.fill(n) { sc.nextLong() }
  def readLineStrings(implicit sc: Scanner): Array[String] = sc.nextLine().split(' ')
  def readLineInts(implicit sc: Scanner): Array[Int] = readLineStrings.map(_.toInt)
  def readLineLongs(implicit sc: Scanner): Array[Long] = readLineStrings.map(_.toLong)

  def main(args: Array[String]): Unit = solve(new Scanner(System.in))

  def mode[T](list: List[T]): (T, Int) = list.groupBy(identity).mapValues(_.size).maxBy(_._2)
  def secondMode[T](list: List[T]): Option[(T, Int)] = list.groupBy(identity).mapValues(_.size).toList.sortBy(_._2).drop(1).headOption

  def solve(implicit sc: Scanner): Unit = {
    val Array(n) = readLineInts
    val v = readLineInts
    val even = v.zipWithIndex.filter { case (_, index) => index % 2 == 0}.map(_._1).toList
    val odd = v.zipWithIndex.filter { case (_, index) => index % 2 == 1}.map(_._1).toList
    val (evenModeElem, evenModeNumber) = mode(even)
    val (oddModeElem, oddModeNumber) = mode(odd)
    if (evenModeElem == oddModeElem) {
      if (evenModeNumber > oddModeNumber) {
        println(n - (evenModeNumber + secondMode(odd).get._2))
      } else if (evenModeNumber < oddModeNumber) {
        println(n - (oddModeNumber + secondMode(even).get._2))
      } else { // evenModeNumber == oddModeNumber
        if (evenModeNumber == (n / 2)) {
          println(evenModeNumber)
        } else {
          throw new NullPointerException
          println(n - (evenModeNumber + Math.max(secondMode(even).get._2, secondMode(odd).get._2)))
        }
      }
    } else {
      println(n - (evenModeNumber + oddModeNumber))
    }
  }
}