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;
use std::str::FromStr;
use std::cmp::max;

fn main(){
    let n: usize = get_one();
    let vs: Vec<usize> = get_vec();
    let mut cnts1 = vec![0;100_001];
    let mut cnts2 = vec![0;100_001];

    let mut i: usize = 0;
    while i < n {
        cnts1[vs[i]] += 1;
        cnts2[vs[i+1]] += 1;
        i += 2;
    }

    let m1 = max_idx(&cnts1);
    let m2 = max_idx(&cnts2);

    if m1 != m2 {
        let ans = n as i64 - cnts1.iter().fold(&0, max) - cnts2.iter().fold(&0, max);
        println!("{}", ans);
    } else {
        cnts1.sort();
        cnts2.sort();
        let a = max(cnts1[(cnts1.len()-2) as usize], cnts2[(cnts2.len()-2) as usize]);
        let ans = n as i64 - cnts1.iter().fold(&0, max).clone() as i64 - a as i64;
        println!("{}", ans);
    }
}

fn max_idx(v: &Vec<i64>) -> usize{
    let mut ret = 0;
    let mut mx = 0;
    for i in 0..v.len() {
        if v[i] > mx {
            ret = i;
            mx = v[i];
        }
    }
    ret
}

#[allow(dead_code)]
fn get_line() -> String {
    let mut s = String::new();
    match stdin().read_line(&mut s){
        Ok(_) => {s.trim().to_string()}
        Err(_) => String::new()
    }
}

#[allow(dead_code)]
fn get_vec<T: std::str::FromStr>() -> Vec<T> {
    let line = get_line();
    line.split_whitespace().filter_map(|x| x.parse().ok()).collect()
}

#[allow(dead_code)]
fn get_one<T: FromStr + Copy>() -> T {
    let v = get_vec();
    v[0]
}

#[allow(dead_code)]
fn get_pair<T: FromStr + Copy>() -> (T, T) {
    let v = get_vec();
    (v[0], v[1])
}

#[allow(dead_code)]
fn get_triple<T: FromStr + Copy>() -> (T, T, T) {
    let v = get_vec();
    (v[0], v[1], v[2])
}

#[allow(dead_code)]
fn get_chars() -> Vec<char> {
    get_line().chars().collect()
}