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: Wrong Answer)

use std::io;
use std::collections::HashMap;
use std::cmp;

fn main() {
    let n = read_one::<usize>();
    let vn = read::<usize>();
    let mut odd = HashMap::new();
    let mut even = HashMap::new();

    for i in 0..n {
        if i % 2 == 0 {
            *even.entry(vn[i]).or_insert(0) += 1;
        } else {
            *odd.entry(vn[i]).or_insert(0) += 1;
        }
    }
    let mut even_key = 0;
    let mut odd_key = 0;
    let mut even_max = 0;
    let mut even_2nd = 0;
    let mut odd_max = 0;
    let mut odd_2nd = 0;
    for (k, v) in even.iter() {
        if *v >= even_max {
            even_key = *k;
            even_2nd = even_max;
            even_max = *v;
        }
    }

    for (k, v) in odd.iter() {
        if *v >= odd_max {
            odd_key = *k;
            odd_2nd = odd_max;
            odd_max = *v;
        }
    }
    
    let diff = if odd_key == even_key {
        cmp::max(odd_2nd + even_max, odd_max + even_2nd)
    } else {
        odd_max + even_max
    };

    let cnt = n - diff;
    println!("{}", cnt);
}


#[allow(unused)]
fn read<T>() -> Vec<T>
where T:
    std::str::FromStr,
    T::Err: std::fmt::Debug {

    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    buf.split_whitespace()
        .map(|s| s.trim().parse().unwrap())
        .collect()
}


#[allow(unused)]
fn read_one<T>() -> T
where T:
    std::str::FromStr,
    T::Err: std::fmt::Debug {

    let mut buf = String::new();
    io::stdin().read_line(&mut buf).unwrap();
    buf.trim().parse().unwrap()
}