// 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("");
}

// 解説読後
// http://yukicoder.me/problems/904/editorial
// めっちゃシンプルなのか・・・

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