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;
use std::str::FromStr;
use std::collections::HashMap;
use std::cmp;
use std::fs::File;

fn input<T:FromStr>() -> T {
    let mut line: String = String::new();
    io::stdin().read_line(&mut line);
    line.trim().parse().ok().unwrap()
}

fn input_vec() -> Vec<u64> {
    let mut line: String = String::new();
    io::stdin().read_line(&mut line);
    line.split_whitespace().map(|s| s.parse().unwrap()).collect()
}

fn main() {
    let n: usize = input();
    let v = input_vec();
    let mut odds: HashMap<u64, u64> = HashMap::new();
    let mut evens: HashMap<u64, u64> = HashMap::new();

    for i in 0..n {
        if i % 2 == 0 {
            let num = evens.entry(v[i]).or_insert(0);
            *num += 1;
        } else {
            let num = odds.entry(v[i]).or_insert(0);
            *num += 1;
        }
    }
    let mut odds_vec: Vec<_> = odds.iter().collect();
    odds_vec.sort_by(|x, y| y.1.cmp(&x.1));
    // println!("{:?}", odds_vec);

    let mut evens_vec: Vec<_> = evens.iter().collect();
    evens_vec.sort_by(|x, y| y.1.cmp(&x.1));
    // println!("{:?}", evens_vec);

    if odds_vec[0].0 == evens_vec[0].0 {
        let mut tmp1 = n as u64 - odds_vec[0].1;
        if evens_vec.len() > 1 {
            tmp1 -= *evens_vec[1].1;
        }

        let mut tmp2 = n as u64 - evens_vec[0].1;
        if odds_vec.len() > 1 {
            tmp2 -= *odds_vec[1].1;
        }
        println!("{}", cmp::min(tmp1, tmp2));
    } else {
        println!("{}", n as u64 - odds_vec[0].1 - evens_vec[0].1);
    }

}