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

t = [0]
sum = 0
i = 1
while sum < 1000000000000001
  sum += 26**i
  t[i] = sum
  i+= 1
end

keta = 0
nokori = 0
1.upto(17) do |i|
  if t[i] >= N
    keta = i
    nokori = N - t[i-1]
    break
  end
end

n = N
ans = []
(keta-1).downto(0) do |i|
  waru = 26**i
  nn = 0
  1.upto(26) do |j|
    if n < waru*j
      nn = j-1
      break
    end
    nn = 26
  end

  ans.push(nn)

  next if nn.zero?

  di = waru * nn

  a=n%di

  n = a
end

al = ('a'..'z').to_a

puts ans.map{|an| al[an-1]}.join('')