def solve():

    n = int(eval(input()))

    a = 97

    tmp = 0

    index = 0

    ans = []

    for i in range(1, 12):

        pre = tmp

        tmp += 26 ** i

        if n <= tmp:

            index = i

            n = n - pre

            break

    n = n - 1

    for _ in range(0, index)[::-1]:

        ans.append(chr((n % 26) + a))

        n = n // 26

    print((''.join(ans[::-1])))

















if __name__ == '__main__':

    solve()

def solve():

    n = int(eval(input()))

    l = 0

    ans = ''

    for i in range(1, 12):

        if n <= 26 ** i:

            l = i

            break

        n = n - 26 ** i

    k = n - 1

    for i in range(l):

        ans = chr(k % 26 + 97) + ans

        k = k // 26



    print(ans)























if __name__ == '__main__':

    solve()

def solve():
    n = int(eval(input()))
    a = 97
    tmp = 0
    index = 0
    ans = []
    for i in range(1, 12):
        pre = tmp
        tmp += 26**i
        if n <= tmp:
            index = i
            n = n - pre
            break
    n = n - 1
    for _ in range(0, index)[::-1]:
        ans.append(chr((n % 26) + a))
        n = n // 26
    print(("".join(ans[::-1])))


if __name__ == "__main__":
    solve()

def solve():
    n = int(eval(input()))
    l = 0
    ans = ""
    for i in range(1, 12):
        if n <= 26**i:
            l = i
            break
        n = n - 26**i
    k = n - 1
    for i in range(l):
        ans = chr(k % 26 + 97) + ans
        k = k // 26
    print(ans)


if __name__ == "__main__":
    solve()

-    a = 97 -    tmp = 0 -    index = 0 -    ans = [] +    l = 0 +    ans = "" -        pre = tmp -        tmp += 26**i -        if n <= tmp: -            index = i -            n = n - pre +        if n <= 26**i: +            l = i -    n = n - 1 -    for _ in range(0, index)[::-1]: -        ans.append(chr((n % 26) + a)) -        n = n // 26 -    print(("".join(ans[::-1]))) +        n = n - 26**i +    k = n - 1 +    for i in range(l): +        ans = chr(k % 26 + 97) + ans +        k = k // 26 +    print(ans)