How can I get the variable to subtract the input please?

[Ed Taylor]

This will be very simple to most of you I guess but it's killing me!

print ("Please type in your age")
age =  input ()
leave = 16
print ("You have" + leave - age + "years left at school")

I want to have an input where the users age is inserted and then subtracted from the variable age which is set to 16 and the answer displayed as You have x years left at school.

Help much appreciated.

Thank you