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: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func mode(nums map[int]int) (int, int) {
	m := 0
	s := 0
	for k, v := range nums {
		if v > nums[m] {
			m = k
		} else {
			s = k
		}
	}
	return m, s
}

func min(n, m int) int {
	if n < m {
		return n
	}
	return m
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())

	l := make([]int, n)
	for i := 0; sc.Scan(); i++ {
		m, _ := strconv.Atoi(sc.Text())
		l[i] = m
	}

	odds := make(map[int]int)
	evens := make(map[int]int)
	for i := 0; i < n; i++ {
		if i%2 == 0 {
			evens[l[i]]++
		} else {
			odds[l[i]]++
		}
	}

	em, es := mode(evens)
	om, os := mode(odds)

	if em == om {
		fmt.Println(min(n/2-evens[es], n/2-odds[os]))
	} else {
		fmt.Println(n - evens[em] - odds[om])
	}

}