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 Rust (1.15.1) (judge verdict: Accepted)

#![allow(unused_mut, non_snake_case,unused_imports,dead_code)]
use std::iter;
use std::cmp::{max, min, Ordering};
use std::mem::{swap};
use std::collections::{HashMap,BTreeMap,HashSet,BTreeSet,BinaryHeap,VecDeque};
use std::iter::FromIterator;

//　高速 EOF要
//macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();input_inner!{iter, $($r)*}};($($r:tt)*) => {let mut s = {use std::io::Read;let mut s = String::new();std::io::stdin().read_to_string(&mut s).unwrap();s};let mut iter = s.split_whitespace();input_inner!{iter, $($r)*}};}
//macro_rules! input_inner {($iter:expr) => {};($iter:expr, ) => {};($iter:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($iter, $t);input_inner!{$iter $($r)*}};}
//macro_rules! read_value {($iter:expr, ( $($t:tt),* )) => {( $(read_value!($iter, $t)),* )};($iter:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()};($iter:expr, chars) => {read_value!($iter, String).chars().collect::<Vec<char>>()};($iter:expr, usize1) => {read_value!($iter, usize) - 1};($iter:expr, $t:ty) => {$iter.next().unwrap().parse::<$t>().expect("Parse error")};}
// 低速 EOF不要
macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();let mut next = || { iter.next().unwrap() };input_inner!{next, $($r)*}};($($r:tt)*) => {let stdin = std::io::stdin();let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));let mut next = move || -> String{bytes.by_ref().map(|r|r.unwrap() as char).skip_while(|c|c.is_whitespace()).take_while(|c|!c.is_whitespace()).collect()};input_inner!{next, $($r)*}};}
macro_rules! input_inner {($next:expr) => {};($next:expr, ) => {};($next:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($next, $t);input_inner!{$next $($r)*}};}
macro_rules! read_value {($next:expr, ( $($t:tt),* )) => {( $(read_value!($next, $t)),* )};($next:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()};($next:expr, chars) => {read_value!($next, String).chars().collect::<Vec<char>>()};($next:expr, usize1) => {read_value!($next, usize) - 1};($next:expr, $t:ty) => {$next().parse::<$t>().expect("Parse error")};}

// 非常時
fn read_line() -> String{ let mut s = String::new(); std::io::stdin().read_line(&mut s).unwrap(); s.trim().to_string() }

/*
 <url:>
 問題文============================================================
 =================================================================
 解説=============================================================
 ================================================================
 */
fn main(){
    input!(n:i32,v:[i32;n]);
    let n:i32 = n;
    let mut v:Vec<i32> = v;

    let mut even = vec![0;100005];
    let mut odd = vec![0;100005];
    for (i,x) in v.into_iter().enumerate(){
        if i%2 == 0 { even[x as usize]+=1;}
        else {odd[x as usize]+=1;}
    }

    let mut a:Vec<_> = (0..100005).collect();
    let mut b:Vec<_> = (0..100005).collect();

    a.sort_by_key(|&i| -even[i]);
    b.sort_by_key(|&i| -odd[i]);

    let mut ans = i32::max_value();
    for i in 0..2{
        for j in 0..2{
            if a[i] != b[j]{
                ans = min(ans,n-even[a[i]] - odd[b[j]]);
            }
        }
    }
    println!("{}",ans);
}