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)

// abc111_c (arc103_a)
use std::cmp::max;

fn read<T: std::str::FromStr>(
    stdin_lock: &mut std::io::StdinLock,
    buf: &mut Vec<u8>,
    delimiter: u8,
) -> T {
    buf.clear();
    let l = std::io::BufRead::read_until(stdin_lock, delimiter, buf).unwrap();
    buf.truncate(l - 1); // remove delimiter
    let s = unsafe { std::str::from_utf8_unchecked(&buf) };
    s.parse().unwrap_or_else(|_| panic!("read"))
}

fn main() {
    let stdin = std::io::stdin();
    let mut stdin_lock = stdin.lock();
    let mut buf: Vec<u8> = Vec::new();
    let n: usize = read(&mut stdin_lock, &mut buf, b'\n');
    let mut vv = vec![0usize; n];
    for i in 0..n - 1 {
        vv[i] = read(&mut stdin_lock, &mut buf, b' ');
    }
    vv[n - 1] = read(&mut stdin_lock, &mut buf, b'\n');

    let mut me = vec![(0usize, 0i32); 100_000 + 1];
    let mut mo = vec![(0usize, 0i32); 100_000 + 1];
    for i in 0..n {
        if i % 2 == 0 {
            me[vv[i]].0 = vv[i];
            me[vv[i]].1 += 1;
        } else {
            mo[vv[i]].0 = vv[i];
            mo[vv[i]].1 += 1;
        }
    }

    me.sort_by(|&(_, v1), &(_, v2)| v2.cmp(&v1));
    mo.sort_by(|&(_, v1), &(_, v2)| v2.cmp(&v1));

    let ans = n as i32
        - if me[0].0 != mo[0].0 {
            me[0].1 + mo[0].1
        } else {
            max(me[0].1 + mo[1].1, me[1].1 + mo[0].1)
        };
    println!("{}", ans);
}