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::prelude::*;

fn input<T: std::str::FromStr>() -> T {
    let stdin = std::io::stdin();
    let token: String = stdin
        .lock()
        .bytes()
        .map(|c| c.unwrap() as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().unwrap()
}

fn main() {
    let n: usize = input();
    let v: Vec<i32> = (0..n).map(|_| input()).collect();

    let mut v0 = vec![];
    let mut v1 = vec![];
    for i in 0..n {
        if i % 2 == 0 {
            v0.push(v[i]);
        } else {
            v1.push(v[i]);
        }
    }
    v0.sort();
    v1.sort();

    let mut a0 = vec![];
    let mut i = 0;
    while i < v0.len() {
        let v = v0[i];
        let mut cnt = 0;
        while i < v0.len() && v0[i] == v {
            cnt += 1;
            i += 1;
        }
        a0.push((v, cnt));
    }
    let mut a1 = vec![];
    let mut i = 0;
    while i < v1.len() {
        let v = v1[i];
        let mut cnt = 0;
        while i < v1.len() && v1[i] == v {
            cnt += 1;
            i += 1;
        }
        a1.push((v, cnt));
    }

    a0.sort_by_key(|&(_, c)| -(c as i32));
    a1.sort_by_key(|&(_, c)| -(c as i32));

    if a0[0].0 != a1[0].0 {
        println!("{}", n - a0[0].1 - a1[0].1);
    } else {
        if a0.len() == 1 && a1.len() == 1 {
            println!("{}", n / 2);
        } else if a0.len() == 1 {
            println!("{}", n - a0[0].1 - a1[1].1);
        } else if a1.len() == 1 {
            println!("{}", n - a0[1].1 - a1[0].1);
        } else {
            let mn = std::cmp::min(n - a0[0].1 - a1[1].1, n - a0[1].1 - a1[0].1);
            println!("{}", mn);
        }
    }
}