c++ program help!!!

The program asks the user to enter a positive int less than 20.

The program reads a value n entered by the user. If the value is not legal, your program

keeps asking the user to enter a integer until the integer is valid.

Then the program prints a diamond with side n.

example, if the user enters 5 for n the program should print the following picture:

if the user enters 4 for n the program should print the following picture: