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 (1.14.1) (judge verdict: Wrong Answer)

package main

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

var scanner = bufio.NewScanner(os.Stdin)

func scanInt() int {
	scanner.Scan()
	txt := scanner.Text()
	n, _ := strconv.Atoi(txt)
	return n
}

type Pair struct {
	First  int
	Second int
}

func main() {
	scanner.Split(bufio.ScanWords)

	n := scanInt()
	vs := make([]int, 0, n)
	for i := 0; i < n; i++ {
		vs = append(vs, scanInt())
	}

	areAllSame := true
	for i := 0; i < n; i++ {
		if vs[i] != vs[0] {
			areAllSame = false
			break
		}
	}
	if areAllSame {
		fmt.Println(n / 2)
		return
	}

	oddMap := map[int]int{}
	evenMap := map[int]int{}

	for i := 0; i < n; i++ {
		if i%2 != 0 {
			oddMap[vs[i]]++
		} else {
			evenMap[vs[i]]++
		}
	}

	odd1, odd2 := Pair{}, Pair{}
	even1, even2 := Pair{}, Pair{}

	for key, count := range oddMap {
		if count > odd1.Second {
			odd1.First = key
			odd1.Second = count
		}
	}
	delete(oddMap, odd1.First)
	for key, count := range oddMap {
		if count > odd1.Second {
			odd2.First = key
			odd2.Second = count
		}
	}

	for key, count := range evenMap {
		if count > even1.Second {
			even1.First = key
			even1.Second = count
		}
	}
	delete(evenMap, even1.First)
	for key, count := range evenMap {
		if count > even2.Second {
			even2.First = key
			even2.Second = count
		}
	}

	if odd1.First != even1.First {
		if n%2 == 0 {
			fmt.Println(n/2 - odd1.Second + n/2 - even1.Second)
		} else {
			fmt.Println(n/2 - odd1.Second + n/2 - even1.Second + 1)
		}
		return
	}

	var on int
	if n%2 == 0 {
		on = n / 2
	} else {
		on = n/2 + 1
	}

	if (on-odd1.Second)+(n/2-even2.Second) < (on-odd2.Second)+(n/2-even1.Second) {
		if n%2 == 0 {
			fmt.Println(n/2 - odd1.Second + n/2 - even2.Second)
		} else {
			fmt.Println(n/2 - odd1.Second + n/2 - even2.Second + 1)
		}
	} else {
		if n%2 == 0 {
			fmt.Println(n/2 - odd2.Second + n/2 - even1.Second)
		} else {
			fmt.Println(n/2 - odd2.Second + n/2 - even1.Second + 1)
		}
	}
}