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: Wrong Answer)

use std::io::*;
use std::str::FromStr;
use std::collections::HashMap;

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 main() {
    let n: u32 = read();
    let s = {
        let mut s = String::new(); // バッファを確保
        std::io::stdin().read_line(&mut s).unwrap(); // 一行読む。失敗を無視
        s.trim_right().to_owned() // 改行コードが末尾にくっついてくるので削る
    };

    let vs: Vec<u32> = {
        let mut ws = s.split_whitespace(); // 空白区切りの単語に分解する
        let mut vs = Vec::new();
        for _ in 0..n {
            vs.push(ws.next().unwrap().parse().unwrap());
        }
        vs
    };

    let mut map1: HashMap<u32, u32> = HashMap::new();
    let mut map2: HashMap<u32, u32> = HashMap::new();
    for (i ,v) in vs.iter().enumerate() {
        if i % 2 == 0 {
            if map1.contains_key(&v) {
                let tmp = map1[v].clone();
                map1.insert(v.clone(), tmp + 1);
            } else {
                map1.insert(v.clone(), 1);
            }
        } else {
            if map2.contains_key(&v) {
                let tmp = map2[v].clone();
                map2.insert(v.clone(), tmp + 1);
            } else {
                map2.insert(v.clone(), 1);
            }
        }
    }
    let mut max1 = 0;
    let mut max1b = 0;
    let mut v1 = 0;
    let mut v1b = 0;
    for (k, v) in &map1 {
        if v > &max1 {
            v1b = v1.clone();
            v1 = k.clone();
            max1b = max1.clone();
            max1 = v.clone();
        }
    }

    let mut max2 = 0;
    let mut max2b = 0;
    let mut v2 = 0;
    let mut v2b = 0;
    for (k, v) in &map2 {
        if v > &max2 {
            v2b = v2.clone();
            v2 = k.clone();
            max2b = max2.clone();
            max2 = v.clone();
        }
    }

    if v1 == v2 {
        if max1 > max2 {
            v2 = v2b;
        } else if max1 == max2 {
            if max2b > max1b {
                v2 = v2b;
            } else if max2b == max1b {
                if v1 != 0 {
                    v1 = v1b;
                } else if v2 != 0 {
                    v2 = v2b;
                } else {
                    v1 = 0;
                }
            } else {
                v1 = v1b;
            }
        } else {
            v1 = v1b;
        }
    }

    let mut ans = 0;
    for (i, v) in vs.iter().enumerate() {
        if i % 2 == 0 && v != &v1 {
            ans += 1;
        } else if i % 2 == 1 && v != &v2 {
            ans += 1;
        }
    }
    println!("{}", ans);
}