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 orgn = n;
    let mut length = 1;
    while n / 26 > 0 {
        length += 1;
        n /= 26;
    }
    let alphabets: Vec<String> = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".chars().map(|c| c.to_string()).collect();
    let mut result: Vec<String> = vec![];
    for i in (0..length).rev() {
        let v = orgn / 26usize.pow(i);
        orgn -= v * 26usize.pow(i);
        let v = v - if i > 0 && v == 1 && i == length-1 { 1 } else { 0 };
        let appends = alphabets[v].clone();
        result.push(appends);
    }
    println!("{}", result.join(""));
}