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 Ruby (2.7.1) (judge verdict: Wrong Answer)

def main
  n = gets.to_i

  name_size = 1
  max_idx = 0
  max_idx_kari = 0
  loop do
    max_idx_kari += 26**name_size
    break if n < max_idx_kari
    max_idx += 26 ** name_size
    name_size += 1
  end
  diff = n - max_idx

  name = ""
  name_size.times do |i|
    if name_size - i - 1 == 0
      first = diff / 26 ** (name_size - i - 1)
      name += (first+96).chr
      diff = diff % 26 ** (name_size - i - 1)
    else
      first = diff / 26 ** (name_size - i - 1)
      name += (first+97).chr
      diff = diff % 26 ** (name_size - i - 1)
    end
  end

  puts name
end

main