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 pair struct {
	k, v int
}

type pairs []pair

func (p pairs) Len() int {
	return len(p)
}

func (p pairs) Less(i, j int) bool {
	return p[i].v > p[j].v
}

func (p pairs) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
}

func main() {
	var n int
	fmt.Scan(&n)

	ma := make(map[int]int, n/2)
	mb := make(map[int]int, n/2)
	var t int
	for i := 0; i < n; i++ {
		fmt.Scan(&t)
		if i%2 == 0 {
			ma[t]++
		} else {
			mb[t]++
		}
	}

	al, bl := make(pairs, n/2), make(pairs, n/2)
	var i int
	for k, v := range ma {
		al[i] = pair{k, v}
		i++
	}
	i = 0
	for k, v := range mb {
		bl[i] = pair{k, v}
		i++
	}

	sort.Sort(al)
	sort.Sort(bl)

	maxA, maxB := al[0], bl[0]
	secondA, secondB := al[1], bl[1]

	if maxA.k == maxB.k {
		if maxA.v == maxB.v {
			if secondA.v < secondB.v {
				maxB = bl[1]
			} else {
				maxA = al[1]
			}
		} else if maxA.v < maxB.v {
			maxA = al[1]
		} else {
			maxB = bl[1]
		}
	}

	fmt.Println(n - maxA.v - maxB.v)
}