// yukicoder My Practice
// author: Leonardone @ NEETSDKASU
use std::io;

fn read_int64() -> i64 {
    let mut val_str = String::new();
    io::stdin().read_line(&mut val_str).ok().expect("");
    return val_str.trim().parse().ok().expect("");
}

fn main() {
    let al : Vec<char> = String::from("ABCDEFGHIJKLMNOPQRSTUVWXYZ").chars().collect();
    let n = read_int64() + 1;
    let mut s : i64 = 1;
    let mut d1 : i64 = 1;
    let mut d2 : i64 = 26;
    let mut ans = String::new();
    loop {
        let idx = (((n - s) % d2) / d1) as usize;
        ans.insert(0, al[idx]);
        d1 = d2;
        d2 *= 26;
        s += d1;
        if s > n { break; }
    }
    println!("{}", ans);
}