# celsius6.py, by chaynes@indiana.edu

def celsius(fahrenheit):
    """
    Return the result of converting the Fahrenheit temperature to celsius.
    
    >>> celsius(32)
    0.0
    >>> celsius(212)
    100.0
    >>>
    """
    return 5.0/9 * (fahrenheit - 32)

def main():
    """
    Repeatedly prompt for tempearture in degrees Fahrenheit
    and print its conversion to degrees Celsius.

    Exit if 'quit' is entered.
    """
    while True:
        text = raw_input("Degrees Fahrenheit, or 'quit': ")
        if text == 'quit':
            return
        f_temp = float(text)
        c_temp = celsius(f_temp)
        print f_temp, "degrees Fahrenheit is", c_temp, "degrees Celsius"
    
if __name__ == '__main__':
    main()