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 OCaml (4.10.0) (judge verdict: Accepted)

let rec solve acc = function
  | 0 -> acc
  | n -> solve (Char.chr (Char.code 'a' + n mod 26) :: acc) (n / 26)

let () = Scanf.scanf "%d" @@ fun n ->
  let pow = Array.make 12 0 in
  pow.(0) <- 1;
  for i = 0 to 10 do
    pow.(i + 1) <- 26 * pow.(i)
  done;
  let rec aux d n (p :: ps) =
    if n < p
    then (d, n)
    else aux (d + 1) (n - p) ps in
  let rec solve acc n = function
    | 0 -> acc
    | d -> solve (Char.chr (Char.code 'a' + n mod 26) :: acc) (n / 26) (d - 1) in
  let (d, n) = aux 0 n @@ Array.to_list pow in
  List.iter print_char @@ solve ['\n'] n d