[Tutor] Question

[Jacob Braig]

I am just starting out coding and decided on python. I am confused with
something I go shooting a lot so i wanted to make some stupid easy
calculator for ammo and slowly build the program up when I understand
python better but the code I have now keeps popping up an error and I don't
understand where i went wrong a little help please.
Here is the code like I said very simple stuff.

"""
 This is a simple program for ammo calculation.
 Created by Jacob
"""
AMMO = " This is how much ammo remains for .40 pistol %s. "

print "Program has started."

ammopistol = raw_input("Enter total ammo before use. ")
ammopused = raw_input("Enter total ammo used. ")
ammopleft = ammopistol - ammopused

print AMMO % (ammopistol, ammopused,) ammoleft

I am having issues with " ammopleft = ammopistol - ammopused "  any idea
where I have gone wrong?