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 PyPy3 (7.3.0) (judge verdict: Accepted)

def main():
    import sys
    input = sys.stdin.readline
    from bisect import bisect_left
    N = int(input())
    if N == 1:
        print("a")
        sys.exit()
    d = [chr(i) for i in range(97, 97+26)]
    X = [0, 26]
    y = 26
    while y < 10**15:
        y *= 26
        X.append(X[-1] + y)
    x = bisect_left(X, N) # 桁数
    a = N - X[x-1] - 1
    ans = []
    while a > 0:
        ans.append(a%26)
        a //= 26
    while len(ans) < x:
        ans.append(0)
    for a in reversed(ans):
        print(d[a], end="")
    print()

if __name__ == '__main__':
    main()