from string import ascii_lowercase

from itertools import accumulate





def solve(string):

    n = int(string)

    t = [0] + [len(ascii_lowercase)**i for i in range(1, 12)]

    *t, = accumulate(t)

    l = 0

    ans = ""

    while t[l] < n:

        l += 1

    n -= t[l - 1] + 1

    for i in range(l - 1):

        j, n = divmod(n, len(ascii_lowercase)**(l - i - 1))

        ans += ascii_lowercase[j]

    ans += ascii_lowercase[n]

    return ans





if __name__ == '__main__':

    import sys

    print((solve(sys.stdin.read().strip())))

from string import ascii_lowercase





def solve(string):

    n = int(string)

    ans = ""

    while n:

        n, c = divmod(n - 1, len(ascii_lowercase))

        ans = ascii_lowercase[c] + ans

    return ans





if __name__ == '__main__':

    import sys

    print((solve(sys.stdin.read().strip())))

from string import ascii_lowercase
from itertools import accumulate


def solve(string):
    n = int(string)
    t = [0] + [len(ascii_lowercase) ** i for i in range(1, 12)]
    (*t,) = accumulate(t)
    l = 0
    ans = ""
    while t[l] < n:
        l += 1
    n -= t[l - 1] + 1
    for i in range(l - 1):
        j, n = divmod(n, len(ascii_lowercase) ** (l - i - 1))
        ans += ascii_lowercase[j]
    ans += ascii_lowercase[n]
    return ans


if __name__ == "__main__":
    import sys

    print((solve(sys.stdin.read().strip())))

from string import ascii_lowercase


def solve(string):
    n = int(string)
    ans = ""
    while n:
        n, c = divmod(n - 1, len(ascii_lowercase))
        ans = ascii_lowercase[c] + ans
    return ans


if __name__ == "__main__":
    import sys

    print((solve(sys.stdin.read().strip())))

-from itertools import accumulate -    t = [0] + [len(ascii_lowercase) ** i for i in range(1, 12)] -    (*t,) = accumulate(t) -    l = 0 -    while t[l] < n: -        l += 1 -    n -= t[l - 1] + 1 -    for i in range(l - 1): -        j, n = divmod(n, len(ascii_lowercase) ** (l - i - 1)) -        ans += ascii_lowercase[j] -    ans += ascii_lowercase[n] +    while n: +        n, c = divmod(n - 1, len(ascii_lowercase)) +        ans = ascii_lowercase[c] + ans