def sliding(word, num=3):
    if not isinstance(word,str):
        raise TypeError('first parameter must be a string')
    if not isinstance(num,int):
        raise TypeError('second parameter must be an integer')
    if not 0 < num <= len(word):
        raise ValueError('second parameter can be at most length of first')

def pairSum(data, goal):
    if not isinstance(goal,int):
        raise TypeError('goal must be an integer')
    if not isinstance(data,list):
        raise TypeError('data must be a list')
    for val in data:
        if not isinstance(val, int):
            raise TypeError('entries of list must be integers')

def toDecimal(string, base):
    if not isinstance(base, int):
        raise TypeError('base must be integral')
    if not 2 <= base <= 10:
        raise ValueError('base must be between 2 and 10')
    if not isinstance(string, str):
        raise TypeError('value must be expressed as a string')
    if len(string) == 0:
        raise ValueError('string must be nonempty')
    for digit in string:
	if not (digit.isdigit() and 0 <= int(digit) < base:
            raise ValueError('invalid digit for given base')

def toDecimal(string, base):
    if not isinstance(base, int):
        raise TypeError('base must be integral')
    if not 2 <= base <= 36:
        raise ValueError('base must be between 2 and 36')
    if not isinstance(string, str):
        raise TypeError('value must be expressed as a string')
    if len(string) == 0:
        raise ValueError('string must be nonempty')
    for digit in string:
        if digit.isdigit():
            if not 0 <= int(digit) < base:
                raise ValueError('invalid digit for given base')
        else:
            if not 10 <= (ord(digit) - ord('A')) < base:
                raise ValueError('invalid digit for given base')