def convert_base(n,b):

    """ convert_base(int,int) -> str
    returns the str representation of n (decimal) in base b
    """

    result = ""
    while n!=0:
        digit = n%b
        n//=b
        result = str(digit)+result

        
    return result

# convert_base above fails for 10<b (why ?)
# it also mishandles n = 0
# these two issues are fixed in the improved function below
# (what happens when b = 1?)
def convert_base_imp(n,b):

    """ convert_base(int,int) -> str
    returns the str representation of n (decimal) in base 2<=b<=36
    """

    assert 2<=b<=36, "base is not in range"

    if n==0:
        return "0"
    
    result = ""
    while n!=0:
        digit = n%b
        n//=b
        result = \
        "0123456789abcdefghijklmnopqrstuvwxyz"[digit]+result

        
    return result