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::str::FromStr;
use std::fmt::Debug;
use std::collections::HashMap;

fn read_as_vec<T>() -> Vec<T>
where T: FromStr, <T as FromStr>::Err : Debug{
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    s.trim().split_whitespace().map(|c| T::from_str(c).unwrap()).collect()

}

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

fn get_max_key_value(map: &HashMap<u32, u32>) -> (u32, u32){
    let mut max = (0, 0);
    for (key, value) in map{
        if max.1 < *value{
            max = (*key, *value);
        }
    }
    max
}

fn main(){
    let n: u32 = read_as_vec()[0];
    let series: Vec<u32> = read_as_vec();

    let mut even = HashMap::new();
    let mut odd  = HashMap::new();

    for i in 0..series.len(){
        if i%2 == 0{
            *even.entry(series[i]).or_insert(0) += 1;
        }else{
            *odd.entry(series[i]).or_insert(0) += 1;            
        }
    }
    /*
    for elem in series.iter().step_by(2){
        *even.entry(*elem).or_insert(0) += 1;
    }

    for elem in series.iter().skip(1).step_by(2){
        *odd.entry(*elem).or_insert(0) += 1;
    }
    */
    let even_max = get_max_key_value(&even);
    let odd_max = get_max_key_value(&odd);
    if even_max.0 != odd_max.0{
        println!("{}", series.len() as u32 - even_max.1 - odd_max.1);
    }else{
        even.remove(&even_max.0);
        odd.remove(&odd_max.0);

        let even_2nd_max = get_max_key_value(&even);
        let odd_2nd_max = get_max_key_value(&odd);
        if even_2nd_max.1 > odd_2nd_max.1{
            println!("{}", series.len() as u32 - odd_max.1 - even_2nd_max.1);
        }else{
            println!("{}", series.len() as u32 - even_max.1 - odd_2nd_max.1);
        }
    }
}