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)

#[allow(unused_macros)]
macro_rules! parse_line {
    ( $t:ty ) => (
        {
            let mut line = String::new();
            ::std::io::stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            iter.next().unwrap().parse::<$t>().unwrap()
        }
    );

    ( $( $t:ty), +) => (
        {
            let mut line = String::new();
            ::std::io::stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            ( $(iter.next().unwrap().parse::<$t>().unwrap()),* )
        }
    );
}

#[allow(unused_macros)]
macro_rules! read_line {
    () => (
        {
            let mut line = String::new();
            ::std::io::stdin().read_line(&mut line).unwrap();
            line.pop();
            line
        }
    )
}

#[allow(unused_macros)]
macro_rules! parse_vec {
    ( $t:ty ) => (
        {
            let mut line = String::new();
            ::std::io::stdin().read_line(&mut line).unwrap();
            let iter = line.split_whitespace();
            iter.map(|v| v.parse::<$t>().unwrap()).collect::<Vec<_>>()
        }
    )
}

fn solve(vs: Vec<usize>) -> usize {
    use std::cmp::max;

    let n = vs.len();
    let mut od = [0; 100000+1];
    let mut ev = [0; 100000+1];

    for (i, &v) in vs.iter().enumerate() {
        if (i % 2 == 1) {
            od[v] += 1;
        } else {
            ev[v] += 1;
        }
    }

    let mut od1=(0,0);
    let mut od2=(0,0);
    let mut ev1=(0,0);
    let mut ev2=(0,0);

    for i in 0..100001 {
        if (od1.0 < od[i]) {
            od2 = od1;
            od1 = (od[i], i);
        } else if (od2.0 < od[i]) {
            od2 = (od[i], i);
        }

        if (ev1.0 < ev[i]) {
            ev2 = ev1;
            ev1 = (ev[i], i);
        } else if (ev2.0 < ev[i]) {
            ev2 = (ev[i], i);
        }
    }

    if (od1.1 != ev1.1) {
        n - od1.0 - ev1.0
    } else {
        n - max(od1.0 + ev2.0, od2.0 + ev1.0)
    }
}

fn main() {
    let _n = parse_line!(usize);
    let vs = parse_vec!(usize);

    println!("{}", solve(vs));
}

#[test]
fn solve_test() {
    assert_eq!(solve(vec![3,1,3,2]), 1);
    assert_eq!(solve(vec![105, 119,105,119,105,119]), 0);
    assert_eq!(solve(vec![1,1,1,1]), 2);
}