from collections import deque

def main():

    n = int(eval(input()))

    c = deque()

    while n:

        n -= 1

        c.appendleft(n % 26)

        n = n // 26

    cs = []

    for ce in c:

        ce += 97

        cec = chr(ce)

        cs.append(cec)

    print(("".join(cs)))



if __name__ == '__main__':

    main()

def main():

    n = int(eval(input()))

    nl = 0

    yokei = 0

    yokei_pre = 0

    while yokei < n:

        nl += 1

        yokei_pre = yokei

        yokei += 26 ** nl



    n -= yokei_pre

    n -= 1

    c = [0] * nl

    for i1 in range(1, nl + 1):

        r = n % 26

        c[-i1] = r

        n = n // 26

    cs = []

    for ce in c:

        ce += 97

        cec = chr(ce)

        cs.append(cec)

    print(("".join(cs)))





if __name__ == '__main__':

    main()

from collections import deque


def main():
    n = int(eval(input()))
    c = deque()
    while n:
        n -= 1
        c.appendleft(n % 26)
        n = n // 26
    cs = []
    for ce in c:
        ce += 97
        cec = chr(ce)
        cs.append(cec)
    print(("".join(cs)))


if __name__ == "__main__":
    main()

def main():
    n = int(eval(input()))
    nl = 0
    yokei = 0
    yokei_pre = 0
    while yokei < n:
        nl += 1
        yokei_pre = yokei
        yokei += 26**nl
    n -= yokei_pre
    n -= 1
    c = [0] * nl
    for i1 in range(1, nl + 1):
        r = n % 26
        c[-i1] = r
        n = n // 26
    cs = []
    for ce in c:
        ce += 97
        cec = chr(ce)
        cs.append(cec)
    print(("".join(cs)))


if __name__ == "__main__":
    main()

-from collections import deque - - -    c = deque() -    while n: -        n -= 1 -        c.appendleft(n % 26) +    nl = 0 +    yokei = 0 +    yokei_pre = 0 +    while yokei < n: +        nl += 1 +        yokei_pre = yokei +        yokei += 26**nl +    n -= yokei_pre +    n -= 1 +    c = [0] * nl +    for i1 in range(1, nl + 1): +        r = n % 26 +        c[-i1] = r