                    _ => '1',
                })
                .collect::<String>()
        })
        .map(|sit| u16::from_str_radix(&sit, 2).unwrap())
        .collect::<Vec<_>>();
    sits.sort();
    let answer = sits
        .windows(2)
        .find(|neighbors| neighbors[1] - neighbors[0] == 2)
        .map(|neighbors| neighbors[0] + 1)
        .unwrap();
    println!("{}", answer);
}