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::*;
use std::str::FromStr;

fn main() {
    let n: usize = read();
    let maxn = 1000010;
    let mut ki: Vec<(usize, usize)> = vec![(0, 0); maxn];
    let mut gu: Vec<(usize, usize)> = vec![(0, 0); maxn];
    for i in 0..maxn {
        ki[i].1 = i;
        gu[i].1 = i;
    }
    for i in 0..n {
        let po: usize = read();
        if i % 2 == 0 {
            ki[po].0 += 1;
        } else {
            gu[po].0 += 1;
        }
    }
    ki.sort();
    gu.sort();
    let l = maxn - 1;
    if ki[l].1 != gu[l].1 {
        println!("{}", n - ki[l].0 - gu[l].0);
    } else {
        println!(
            "{}",
            n - std::cmp::max(ki[l].0 + gu[l - 1].0, ki[l - 1].0 + gu[l].0)
        );
    }
}

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")
}