def int_checker():
    """Checks if an integer is more than or equal to 13"""

    error = "enter an integer more than or 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
game_goal = int_checker()
print(game_goal)