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 (1.42.0) (judge verdict: Wrong Answer)

use std::io::*;
use std::str::FromStr;
use std::cmp;
use std::collections::HashMap;
use std::collections::HashSet;
use std::char;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char) 
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

fn read_tuple2<T: FromStr, S: FromStr>() -> (T, S) {
    let a = read();
    let b = read();
    (a, b)
}

fn main() {
    let n:u64 = read();
    let ax:Vec<u64> = (0..n).map(|_|read()).collect();
    let mut s = HashSet::new();
    let mut ans = 0;
    for a in &ax {
        s.insert(a);
    }
    if s.len() == 1 {
        println!("{}", n / 2);
        return;
    }
    let mut num_count = HashMap::new();
    // 0, 2, 4...
    for i in (0..).map(|n|n *2).take_while(|a|*a < n) {
        let n = num_count.entry(ax[i as usize]).or_insert(0);
        *n += 1;
    }
    let mut max_num = 0;
    let mut max_key = 0;
    for key in num_count.keys() {
        let val = num_count[key];
        if val > max_num {
            max_key = *key;
            max_num = val;
        }
    }
    for key in num_count.keys() {
        if max_key != *key {
            ans += num_count[key];
        }
    }

    let mut num_count = HashMap::new();
    // 1, 3, 5...
    for i in (0..).map(|n|n *2 + 1).take_while(|a|*a < n) {
        let n = num_count.entry(ax[i as usize]).or_insert(0);
        *n += 1;
    }
    let mut max_num = 0;
    let mut max_key = 0;
    for key in num_count.keys() {
        let val = num_count[key];
        if val > max_num {
            max_key = *key;
            max_num = val;
        }
    }
    for key in num_count.keys() {
        if max_key != *key {
            ans += num_count[key];
        }
    }
    println!("{}", ans);






}