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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
	"sort"
)

type Num struct {
	Key   int
	Value int
}
type Nums []Num

func (n Nums) Len() int {
	return len(n)
}

func (n Nums) Less(i, j int) bool {
	return n[i].Value > n[j].Value
}

func (n Nums) Swap(i, j int) {
	n[i], n[j] = n[j], n[i]
}

func main() {
	var n int
	fmt.Scan(&n)
	arr := make([]int, n)
	for i := range arr {
		fmt.Scan(&arr[i])
	}
	even := map[int]int{}
	odd := map[int]int{}
	for i := 0; i < n; i++ {
		if i%2 == 0 {
			even[arr[i]]++
		} else {
			odd[arr[i]]++
		}
	}
	var evens Nums
	for k, v := range even {
		evens = append(evens, Num{k, v})
	}
	sort.Sort(Nums(evens))
	if len(evens) < 2 {
		evens = append(evens, Num{})
	}
	var odds Nums
	for k, v := range odd {
		odds = append(odds, Num{k, v})
	}
	sort.Sort(Nums(odds))
	if len(odds) < 2 {
		odds = append(odds, Num{})
	}
	r := 0
	om := 0
	for i := 0; i < len(odds); i++ {
		if odds[i].Key != evens[0].Key {
			om = odds[i].Value
			break
		}
	}
	em := 0
	for i := 0; i < len(evens); i++ {
		if evens[i].Key != odds[0].Key {
			em = evens[i].Value
			break
		}
	}
	l := n / 2
	if evens[0].Value+om >= odds[0].Value+em {
		r = (l - evens[0].Value) + (l - om)
	} else {
		r = (l - odds[0].Value) + (l - em)
	}
	fmt.Println(r)
}