Can you help me with this C++ question?

Can you help me with this C++ question? Entire code should be in the main function.

Factorial: Read an integer N from the user then display the factorial of this number, N!. Note that, the factorial of a negative number is undefined. In case the user enters a negative number, the program should notify the user and then ask him to enter a positive number instead. Recall that, N! = N * (N-1)* (N-2)* ... * 2 * 1 Example: Please enter a positive number: 6 The factorial of 6 is: 6! = 720