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)

// https://atcoder.jp/contests/arc103/tasks/arc103_a

use std::collections::HashMap;

// https://qiita.com/penguinshunya/items/cd96803b74635aebefd6
fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}
fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

fn main() {
    let n = read::<i32>();
    let ais = read_vec::<i32>();
    if n == 2 {
        if ais[0] == ais[1] {
            println!("1")
        } else {
            println!("0")
        }
        return;
    }
    let mut even_histgram: HashMap<i32, i32> = Default::default();
    let mut odd_histgram: HashMap<i32, i32> = Default::default();
    for i in 0..ais.len() {
        let hist = if i % 2 == 0 {
            &mut even_histgram
        } else {
            &mut odd_histgram
        };
        let key = ais[i];
        if hist.get(&key).is_some() {
            *hist.get_mut(&key).unwrap() += 1
        } else {
            hist.insert(key, 1);
        }
    }
    let mut even_histgram_pair: Vec<(i32, i32)> = even_histgram.clone().into_iter().collect();
    let mut odd_histgram_pair: Vec<(i32, i32)> = odd_histgram.clone().into_iter().collect();
    even_histgram_pair.sort_by(|lhs, rhs| rhs.1.cmp(&lhs.1));
    odd_histgram_pair.sort_by(|lhs, rhs| rhs.1.cmp(&lhs.1));
    let count = if even_histgram_pair[0].0 != odd_histgram_pair[0].0 {
        n - even_histgram_pair[0].1 - odd_histgram_pair[0].1
    } else {
        if even_histgram_pair.len() <= 1 && odd_histgram_pair.len() <= 1 {
            n / 2
        } else if even_histgram_pair.len() <= 1 {
            n / 2 - odd_histgram_pair[1].1
        } else if odd_histgram_pair.len() <= 1 {
            n / 2 - even_histgram_pair[1].1
        } else {
            std::cmp::min(
                n - even_histgram_pair[1].1 - odd_histgram_pair[0].1,
                n - even_histgram_pair[0].1 - odd_histgram_pair[1].1,
            )
        }
    };
    println!("{}", count);
}