3 second rule

I gave E a bag of M&M's last night. Right before bed and after brushing her teeth she comes out with something in her mouth. I asked her what it was and of course it was a stray M&M that she had found on the floor. I told her that she wasn't supposed to eat things off the floor. She asked why and I explained that things off the floor were usually dirty. She says ok. Then takes the M&M out of her mouth and throws it on the floor...of course.
This brings up another difficult topic for a 3 year old. We don't throw things on the floor. Why ? she asks. Because it makes the house dirty. So, what does the little stinker do? She picks the M&M up with her TOES and puts it back in her mouth. By that point I gave up and just let her finish the M&M...I love being a parent.