def convertbase(num, n):
    """
    Change a number in base 10 to a base-n number.
    Up to base-36 is supported without special notation.
    """
    num_rep = {(10): 'a', (11): 'b', (12): 'c', (13): 'd', (14): 'e', (15):
        'f', (16): 'g', (17): 'h', (18): 'i', (19): 'j', (20): 'k', (21):
        'l', (22): 'm', (23): 'n', (24): 'o', (25): 'p', (26): 'q', (27):
        'r', (28): 's', (29): 't', (30): 'u', (31): 'v', (32): 'w', (33):
        'x', (34): 'y', (35): 'z'}
    digits = []
    current = num
    while current != 0:
        remainder = current % n
        if remainder < 10:
            digit = str(remainder)
        elif remainder < 36:
            digit = num_rep[remainder]
        else:
            digit = '(' + str(remainder) + ')'
        digits.append(digit)
        current = int(current / n)
    return ''.join(reversed(digits))
