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 Python (3.8.2) (judge verdict: Wrong Answer)

def num_to_str(N):
    # Nが26の何桁になるかをcheck(N^a)
    a = 0
    while True:
        if N > 26 ** a:
            a += 1
        else:
            break
#     print(f"a: {a}")
    
    # x1 * (26 ** a) + x2 * (26 ** (a-1)) + ... + xa * (26 ** 0)
    x_list = []
    if a == 1 or a == 0:
        x_list = [N]
    else:
        for i in range(1, a):
#           print("N:", N)
            b = a - i
            x_i = N // 26 ** b
            x_0 = N % 26 ** b
            
            x_list.append(x_i)
            N -= x_i * 26 ** b
        x_list.append(x_0)
#     print(f"x_list1: {x_list}")
    x_list2 = x_list.copy()
    for i, n in enumerate(x_list):
        if n == 0:
            x_list2[i - 1] += -1
            x_list2[i] = 26
#     print(f"x_list2: {x_list2}")
    
    ans = ""
    for n in x_list2:
        n2 = ord("a") + n - 1
        ans += chr(n2)
    
    return ans
n_input = int(input())
print(num_to_str(n_input))