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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    val xs = readLine()!!.split(" ").map(String::toInt)

    if (xs.toSet().size == 1) {
        println(n / 2)
        return
    }

    val oddNumList = xs.withIndex().filter { it.index % 2 == 0 }.map { it.value }
    val evenNumList = xs.withIndex().filter { it.index % 2 != 0 }.map { it.value }

    val groupby1 = oddNumList.groupBy { it }.map { it.value }.sortedByDescending { it.size }
    val groupby2 = evenNumList.groupBy { it }.map { it.value }.sortedByDescending { it.size }

    val listOfMax1 = groupby1.first()
    val listOfMax2 = groupby2.first()

    if (listOfMax1.first() != listOfMax2.first()) {

        val freq1 = listOfMax1.first()
        val freq2 = listOfMax2.first()

        val count1 = groupby1.filter { it[0] != freq1 }.sumBy { it.size }
        val count2 = groupby2.filter { it[0] != freq2 }.sumBy { it.size }

        println(count1 + count2)
        return
    }


    val freq1 = listOfMax1.first()
    val freq2 = groupby2[1].first()
    val count1 = groupby1.filter { it[0] != freq1 }.sumBy { it.size }
    val count2 = groupby2.filter { it[0] != freq2 }.sumBy { it.size }
    val ans1 = count1 + count2

    val freq3 = groupby1[1].first()
    val freq4 = listOfMax2.first()
    val count3 = groupby1.filter { it[0] != freq3 }.sumBy { it.size }
    val count4 = groupby2.filter { it[0] != freq4 }.sumBy { it.size }
    val ans2 = count3 + count4

    if (ans1 < ans2) {
        println(ans1)
    } else {
        println(ans2)
    }
}