Problem:
Score : 300 points

Problem Statement

1000000000000001 dogs suddenly appeared under the roof of Roger's house, all of which he decided to keep. The dogs had been numbered 1 through 1000000000000001, but he gave them new names, as follows:

the dogs numbered 1,2,\cdots,26 were respectively given the names a, b, ..., z;

the dogs numbered 27,28,29,\cdots,701,702 were respectively given the names aa, ab, ac, ..., zy, zz;

the dogs numbered 703,704,705,\cdots,18277,18278 were respectively given the names aaa, aab, aac, ..., zzy, zzz;

the dogs numbered 18279,18280,18281,\cdots,475253,475254 were respectively given the names aaaa, aaab, aaac, ..., zzzy, zzzz;

the dogs numbered 475255,475256,\cdots were respectively given the names aaaaa, aaaab, ...;

and so on.

To sum it up, the dogs numbered 1, 2, \cdots were respectively given the following names:

a, b, ..., z, aa, ab, ..., az, ba, bb, ..., bz, ..., za, zb, ..., zz, aaa, aab, ..., aaz, aba, abb, ..., abz, ..., zzz, aaaa, ...

Now, Roger asks you:

"What is the name for the dog numbered N?"

Constraints

N is an integer.

1 \leq N \leq 1000000000000001

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer to Roger's question as a string consisting of lowercase English letters.

Sample Input 1

2

Sample Output 1

b

Sample Input 2

27

Sample Output 2

aa

Sample Input 3

123456789

Sample Output 3

jjddja

Solution in Rust (1.42.0) (judge verdict: Accepted)

#![allow(unused_macros)]
#![allow(dead_code)]
#![allow(unused_imports)]

use itertools::Itertools;
use proconio::*;
use std::collections::VecDeque;
use std::io::stdin;
use std::str::FromStr;
use text_io::*;

const U_INF: usize = 1 << 60;
const I_INF: isize = 1 << 60;

fn main() {
    let mut sc = Scanner::new();
    let n = sc.next_usize();
    let mut n = n;
    let mut s = String::new();

    while n != 0 {
        let a = n / 26;
        let b = (n % 26) as u8;
        n = a;
        // eprintln!("{:?}", (a, b));
        let b = if b == 0 {
            n -= 1;
            25
        } else {
            b - 1
        };
        s.push((b'a' + b) as char);
    }

    println!("{}", s.chars().rev().collect::<String>());
}

pub struct Scanner {
    buf: VecDeque<String>,
}

impl Scanner {
    pub fn new() -> Self {
        Self {
            buf: VecDeque::new(),
        }
    }

    fn scan_line(&mut self) {
        let mut flag = 0;
        while self.buf.is_empty() {
            let mut s = String::new();
            stdin().read_line(&mut s).unwrap();
            let mut iter = s.split_whitespace().peekable();
            if iter.peek().is_none() {
                if flag >= 5 {
                    panic!("There is no input!");
                }
                flag += 1;
                continue;
            }

            for si in iter {
                self.buf.push_back(si.to_string());
            }
        }
    }

    pub fn next<T: FromStr>(&mut self) -> T {
        self.scan_line();
        self.buf
            .pop_front()
            .unwrap()
            .parse()
            .unwrap_or_else(|_| panic!("Couldn't parse!"))
    }

    pub fn next_usize(&mut self) -> usize {
        self.next()
    }

    pub fn next_isize(&mut self) -> isize {
        self.next()
    }

    pub fn next_chars(&mut self) -> Vec<char> {
        self.next::<String>().chars().collect_vec()
    }

    pub fn next_string(&mut self) -> String {
        self.next()
    }

    pub fn fill_vec_line<T: FromStr>(&mut self, v: &mut Vec<T>) {
        for vi in v {
            *vi = self.next();
        }
    }

    pub fn fill_vec<T: FromStr>(&mut self, v: &mut Vec<Vec<T>>) {
        for vi in v {
            for vii in vi {
                *vii = self.next();
            }
        }
    }

    pub fn make_vec_line<T: FromStr + Default + Clone>(&mut self, i: usize) -> Vec<T> {
        let mut v = vec![Default::default(); i];
        self.fill_vec_line(&mut v);
        v
    }

    pub fn make_vec<T: FromStr + Default + Clone>(&mut self, i: usize, j: usize) -> Vec<Vec<T>> {
        let mut v = vec![vec![Default::default(); j]; i];
        self.fill_vec(&mut v);
        v
    }
}