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: Accepted)

def input_n
  gets.to_i               # 単一整数
end

def input_s
  gets.chomp              # 文字列。chompを付けないと改行文字がついてくる
end

def input_a
  gets.split.map(&:to_i)  # スペースで区切られた複数の整数
end

def input_o(num)
  num.times.map { gets.to_i }  # 縦に並んだ複数の整数。たまにある
end

def output_f(num)
  puts sprintf("%.12f", num)
end

def num_to_char(num)
  return "a" if num == 1
  return "b" if num == 2
  return "c" if num == 3
  return "d" if num == 4
  return "e" if num == 5
  return "f" if num == 6
  return "g" if num == 7
  return "h" if num == 8
  return "i" if num == 9
  return "j" if num == 10
  return "k" if num == 11
  return "l" if num == 12
  return "m" if num == 13
  return "n" if num == 14
  return "o" if num == 15
  return "p" if num == 16
  return "q" if num == 17
  return "r" if num == 18
  return "s" if num == 19
  return "t" if num == 20
  return "u" if num == 21
  return "v" if num == 22
  return "w" if num == 23
  return "x" if num == 24
  return "y" if num == 25
  return "z" if num == 0
end

n = input_n
str = ""

(1..99).each do |i|
  if n <= 26 ** i
    n -= 1
    i.times do |j|
      # str << num_to_char(n % 26)
      str << ("a".ord + n % 26).chr
      n = n / 26
    end
    break
  else
    n -= 26 ** i
  end
end

str = str.reverse

puts str