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: Time Limit Exceeded)

n = getter = -> {
  require "stringio"
  _in = StringIO.new
  while l = gets
    _in << l
  end
  _in.string
}.call.to_i

module Permu
  module_function
  @a = ("a".."z").to_a

  def name(n)
    pos, _p = ordercheck(n)
    pos = 1 if pos == 0
    val = _p.find { |e, i|
      i == pos - 1
    }
    val[0].join("")
  end

  def ordercheck(num)
    cnt = 0
    n = num.clone
    size = 0
    loop do
      size = (@a.size ** (cnt += 1))
      break if n <= size
      n -= (size)
    end
    _p = @a.repeated_permutation(cnt).with_index
    if n > size.div(2)
      _p = _p.reverse_each
    end
    return n, _p
  end
end

puts Permu.name(n)