fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let mut n: usize = n.trim().parse().unwrap();

    let mut c: Vec<char> = ('A'..='Z').collect();
    let mut answer = vec![];

    loop {
        answer.push(c[n % c.len()]);
        n /= c.len();
        if n == 0 {
            break;
        }
        if c.len() == 26 {
            c.reverse();
            c.push('A');
            c.reverse();
        }
    }

    answer.reverse();
    let answer: String = answer.iter().collect();

    println!("{answer}");
}