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: Wrong Answer)

use std::io::*;
use std::str::FromStr;

//https://qiita.com/tubo28/items/e6076e9040da57368845
fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char)
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}

//https://onlinejudge.u-aizu.ac.jp/solutions/problem/ALDS1_5_B/review/2709881/arsenic28/Rust
trait Joinable {
    fn join(self, sep: &str) -> String;
}

impl<U: ToString, T: Iterator<Item = U>> Joinable for T {
    fn join(self, sep: &str) -> String {
        self.map(|x| x.to_string()).collect::<Vec<_>>().join(sep)
    }
}

fn set_moji(n:usize) -> char{
    let res = match n {
        1 => 'a',
        2 => 'b',
        3 => 'c',
        4 => 'd',
        5 => 'e',
        6 => 'f',
        7 => 'g',
        8 => 'h',
        9 => 'i',
        10 => 'j',
        11 => 'k',
        12 => 'l',
        13 => 'm',
        14 => 'n',
        15 => 'o',
        16 => 'p',
        17 => 'q',
        18 => 'r',
        19 => 's',
        20 => 't',
        21 => 'u',
        22 => 'v',
        23 => 'w',
        24 => 'x',
        25 => 'y',
        26 => 'z',
        _ => 'a',
    };
    res
}

fn main() {
    let n:u64 = read();

    let mut range_n = 0;
    let mut mojisuu = 1;
    for i in 1..12{
        if n < range_n{
            mojisuu = i-1;
            //println!("range_n{} {}moji",range_n,mojisuu);
            break;
        }else{
            range_n += 26u64.pow(i);
        }
    }    

    let mut top_n = n;
    for i in 1..mojisuu{
        //println!("top_n{} pow{}",top_n,26u64.pow(i));
        top_n -= 26u64.pow(i);
    }

    let mut d_n = top_n;
    let mut ans = Vec::new();


    while mojisuu != 0{
        for i in 1..27{
            if d_n <= 26u64.pow(mojisuu-1){
                ans.push(set_moji(i));
                mojisuu -= 1;
                break;
            }else{
                d_n -= 26u64.pow(mojisuu-1);
            }
        }
    }

    //println!("d_n{}",d_n);
    println!("{}",ans.iter().join(""));
    

}