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)

n = gets.chomp.to_i - 1
ab = 'abcdefghijklmnopqrstuvwxyz'

keta_shikiis = [26, 702, 18278, 475254, 12356630, 321272406, 8353082582, 217180147158, 5646683826134, 146813779479510, 3817158266467286]
#        1000000000000001
# ruijos = [141167095653376, 5429503678976, 208827064576, 8031810176, 308915776, 11881376, 456976, 17576, 676, 26]
name = []

keta_index = keta_shikiis.bsearch_index{|v| v > n }
n -= keta_shikiis[keta_index - 1] if keta_index > 0

if n == 0
  puts 'a' * (keta_index + 1)
else
  while n != 0
    amari = n % 26
    name.push(ab[amari])
    # p [n, name]
    n = (n - amari) / 26
  end

  puts name.reverse.join('')
end