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)

use proconio::input;

fn main() {
    input! {
        n: i64,
    };

    let (l, m) = {
        let mut l = 0;
        let mut m = 0;
        while m < n {
            l += 1;
            m += 26_i64.pow(l);
        }
        (l, m - 26_i64.pow(l))
    };
    let ans = {
        let mut n = n - m - 1; // shadowing
        let mut s = vec![];
        for _ in 0..l {
            s.push(((n % 26) as u8 + b'a') as char);
            n /= 26;
        }
        s.iter().rev().collect::<String>()
    };
    println!("{}", ans);

    // let mut s = vec![];
    // while n > 0 {
    //     n -= 1;
    //     s.push(((n % 26) as u8 + b'a') as char);
    //     n /= 26;
    // }
    // println!("{}", s.iter().rev().collect::<String>());
}