I have tried making the input an integer but if I put a letter in I get the 'invalid literal for an int'

Please could you help.

```
def agecheck():

    quit_menu = False

    while quit_menu is False:

         age = input("\nEnter your age: ")

         if age >= "18":
             print("You are the correct age.")
         elif age < "18":
             print("Get off this website.")
         else:
             print("Enter a correct integer.")
             quit_menu = True

    agecheck()

```