import math
print
def hello():
    print("Hello!")

def area(width, height):
    return width * height
def welcome(name):
    print("Welcome,", name)
def circle(radius):
    return math.pi * radius ** 2
def square(width):
    return area( width , width)
def pos_input(prompt):
    number = float(input(prompt))
    while number <= 0:
        print("The number must be positive.")
        number = float(input(prompt))
    return number

def options():
    print("To calculate the area of a square, press s.")
    print("To calculate the area of a rectangle, press r.")
    print("To calculate the area of a circle, press c.")
    print("To quit, press q.")

name = input("Your name: ")
hello()
welcome(name)
options()
choice = "x"

while choice != "q":
    choice = input("Please enter your choice: ")
    if choice == "s":
        width = pos_input("Length of square side: ")
        print("The area of this square is", square(width))
        options()

    elif choice == "r":
        width = pos_input("Please enter the width of the rectangle: ")
        height = pos_input("Please enter the height of the rectangle: ")
        print("The area of the rectangle is:", area(width, height))
        options()
    elif choice == "c":
        radius = pos_input("Please enter the radius of the circle: ")
        print("The area of the circle is", circle(radius))
        options()
    elif choice != "q":
        print("Invalid choice.")
        options()