use itertools::Itertools;

#[cfg(debug_assertions)]
const INPUT: usize = 10000;
#[cfg(debug_assertions)]
const LENGTH: usize = 20;

#[cfg(not(debug_assertions))]
const INPUT: usize = 10011111011011001;
#[cfg(not(debug_assertions))]
const LENGTH: usize = 272;
const LENGTH2: usize = 35651584;

fn main() {
    calculate_checksum(LENGTH);
    calculate_checksum(LENGTH2);
}

fn calculate_checksum(length: usize) {
    let mut a = INPUT.to_string();
    while a.len() < length {
        let mut b = a.clone();
        b = b
            .chars()
            .rev()
            .map(|c| if c == '0' { '1' } else { '0' })
            .collect();

        let mut result = a.clone();
        result.push('0');
        result.push_str(&b);
        a = result;
    }
    a.truncate(length);

    loop {
        let possible_checksum: String = a
            .chars()
            .tuples()
            .map(|(c0, c1)| c0 == c1)
            .map(|b| if b { '1' } else { '0' })
            .collect();
        if possible_checksum.len() % 2 == 1 {
            a = possible_checksum;
            break;
        }
        a = possible_checksum;
    }
    println!("{a}");
}