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 PyPy2 (7.3.0) (judge verdict: Accepted)

from math import log, ceil
r = 26
ab = "abcdefghijklmnopqrstuvwxyz"
input = raw_input
n = int(input())

def answer(n):
    m = int(ceil(log(n*(r-1) + r, r))) - 1

    #cur = r ** (m-1)
    out = ""

    sub = (r ** m - r) // (r-1)
    n = n - sub - 1
    for i in range(m):
        i = n % r
        out = ab[i] + out
        n //= r
        #i = n // cur
        #out = out + ab[i-1]
        #n -= i * cur
        #cur //= r
    return out

#for n in range(1, 676 + 26 + 2):
if True:
    out = answer(n)
    #print(n, out)
    print(out)