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)

use std::io::{stdin, Read};
use std::str::FromStr;

// https://qiita.com/tubo28/items/e6076e9040da57368845
fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

#[allow(dead_code)]
fn main() {
    let n = read::<usize>();
    let vv = (0..n).map(|_| read::<usize>()).collect::<Vec<_>>();
    use std::collections::HashMap;
    let mut odds: HashMap<usize, i32> = HashMap::new();
    let mut evens: HashMap<usize, i32> = HashMap::new();

    for i in 0..n {
        let v = vv[i];
        if i % 2 == 0 {
            let &c = evens.get(&v).or(Some(&0)).unwrap();
            evens.insert(v, c + 1);
        } else {
            let &c = odds.get(&v).or(Some(&0)).unwrap();
            odds.insert(v, c + 1);
        }
    }

    let mut ve = evens.iter().map(|(&k, &v)| (v, k)).collect::<Vec<_>>();
    ve.sort();

    let mut vo = odds.iter().map(|(&k, &v)| (v, k)).collect::<Vec<_>>();
    vo.sort();

    let e_len = ve.len();
    let o_len = vo.len();
    let (c1, v1) = ve[e_len - 1];
    let (c3, v3) = vo[o_len - 1];

    let a: i32 = vo.iter().map(|&(c, v)| c).sum();
    let b: i32 = ve.iter().map(|&(c, v)| c).sum();

    if v1 != v3 {
        let (e1, _) = ve[e_len - 1];
        let (o1, _) = vo[o_len - 1];
        println!("{}", a + b - e1 - o1);
    } else {
        let (e1, _) = ve[e_len - 1];
        let (o1, _) = vo[o_len - 1];

        if e_len == 1 && o_len == 1 {
            println!("{}", n / 2);
        } else if e_len == 1 {
            let (o2, _) = vo[o_len - 2];
            println!("{}", a + b - e1 - o2);
        } else if o_len == 1 {
            let (e2, _) = ve[e_len - 2];
            println!("{}", a + b - e2 - o1);
        } else {
            let (e2, _) = ve[e_len - 2];
            let (o2, _) = vo[o_len - 2];
            use std::cmp::min;
            let ans = min(a + b - e1 - o2, a + b - e2 - o1);
            println!("{}", ans);
        }
    }
}