need help writing this Fortran code

Write a Fortran program that prompts the user for an integer called DDC whose values should be between 0 and 999, inclusive. Check that the user has entered a value in that range and print an error if he didn't. Using cascaded if statements, convert that number into a string, according to the following system and store the string in a string (character array) variable. Print the value of the stored character variable as the Dewey Decimal Class