@staticmethod
def c():
    n = int(sys.stdin.readline().rstrip())
    n -= 1
    l = 1
    while True:
        if (n < pow(26, l)):
            break
        n -= pow(26, l)
        l += 1
    res = ''.join([chr((ord('a') + d)) for d in NumberTheory.base_convert(n, 26)][::(- 1)])
    res = (('a' * (l - len(res))) + res)
    print(res)
@staticmethod
def c():
    n = int(sys.stdin.readline().rstrip())
    n -= 1
    l = 1
    while True:
        if (n < pow(26, l)):
            break
        n -= pow(26, l)
        l += 1
    res = .join([chr((ord('a') + d)) for d in NumberTheory.base_convert(n, 26)][::(- 1)])
    res = (('a' * (l - len(res))) + res)
    print(res)