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::Read;
use std::collections::HashMap;


fn freq(a: &Vec<i32>) -> Vec<(i32,usize)> {
    let mut h: HashMap<i32,usize> = HashMap::new();
    for x in a {
        let v = h.entry(*x).or_insert(0);
        *v += 1;
    }
    let mut a: Vec<_> = h.into_iter().collect();
    a.sort_by_key(|x| x.1);
    a.reverse();
    let len = a.len();
    a.resize(std::cmp::min(2, len), (0,0));
    a.push((0,0));
    a
}

fn main() {
    let mut buf = String::new();

    std::io::stdin().read_to_string(&mut buf).unwrap();

    let mut iter = buf.split_whitespace();
    let n: i32 = iter.next().unwrap().parse().unwrap();
    let mut v0 = Vec::new();
    let mut v1 = Vec::new();
    for i in 0..n {
        let x: i32 = iter.next().unwrap().parse().unwrap();
        if i % 2 == 0 {
            v0.push(x);
        }else {
            v1.push(x);
        }
    }
    let mut ans = std::i32::MAX;
    for (g0,f0) in freq(&v0) {
        for (g1,f1) in freq(&v1) {
            if g0 == g1 {
                continue;
            }
            let sub = v0.len() + v1.len() - f0 - f1;
            ans = std::cmp::min(ans, sub as i32);
        }
    }
    println!("{}", ans);
}