# functions go here

# usage
def yes_no(question):

    while True:
        response = input(question).lower()

        # check the user says yes / no / y / n
        if response == "yes" or response == "y":
            return "yes"
        elif response == "no" or response == "n":
            return "no"
        else:
            print("please enter yes / no")


def instructions():
   """ Prints instructions """
   print("""
   *** Instructions ****
   Roll the dice and try to win!
   """)

def int_check():
    """Checks users enter an integer more than / equal to 13"""

    error = "Please enter an integer more than / equal to 13."

    while True:
        try:
            response = int(input("What is the game goal? "))

            if response < 13:
                print(error)
            else:
                return response

        except ValueError:
            print(error)
# Main routine

want_instructions = yes_no("Do you want to see the instructions? ")

if want_instructions == "yes":
    instructions()

game_goal = int_check()
print(game_goal)