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: Wrong Answer)

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

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

    var memo = mutableMapOf<Pair<Int, Int>, Int>()
    for ((i, v) in vs.withIndex()) {
        if (vs.size - 2 <= i) {
            break
        }

        if (vs[i] == vs[i+2]) {
            continue
        }

        var pair = Pair(vs[i], vs[i+2])
        if (memo.containsKey(pair)) {
            var c = memo[pair]!!
            memo[pair] = c++
        } else {
            memo[pair] = 1
        }
    }

    if (memo.isEmpty()) {
        println(0)
        return
    }

    println(memo.size)
}