Let's create a C++ program for a shape calculator that uses function overloading to calculate the area of different shapes (rectangle, circle, and triangle). These functions will have the same name but will be able to calculate area for different types of figures.

Your task is to create overloaded calculateArea() functions. All arguments must have double type:

• The first function must have two positional arguments, length and width (the order of arguments must be the same!).
• The second function must have one argument named radius.
• The third function must have three arguments, a, b and c. These arguments represent the length of all sides of the triangle.