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 "fmt"

// 2018-10-25T16:28:48+0800
// 2018-10-25T16:43:57+0800
func main() {
	var n int
	fmt.Scanf("%d", &n)
	//v := make([]int, n)
	a := make([]int, n/2)
	b := make([]int, n/2)
	ma := make(map[int]int, n/2)
	aa1 := -1
	aa2 := -1
	mb := make(map[int]int, n/2)
	bb1 := -1
	bb2 := -1
	for i := 0; i < n/2; i++ {
		fmt.Scanf("%d", &a[i])
		ma[a[i]]++
		if ma[a[i]] > ma[aa1] {
			aa2 = aa1
			aa1 = a[i]
		}
		fmt.Scanf("%d", &b[i])
		mb[b[i]]++
		if mb[b[i]] > mb[bb1] {
			bb2 = bb1
			bb1 = b[i]
		}
	}
	if aa1 != bb1 {
		fmt.Println(n - ma[aa1] - mb[bb1])
		return
	}
	O1 := n - ma[aa1] - mb[bb2]
	O2 := n - ma[aa2] - mb[bb1]
	if O1 > O2 {
		fmt.Println(O2)
	} else {
		fmt.Println(O1)
	}
}