Sven and Ollie live in the same apartment building in identical flats. Sven visits Ollie and sees that he just painted his flat and it looks great. “He says, “Ollie, this looks amazing. How many cans of paint did you buy?” Ollie says he bought seven. …..

The next day Sven drives to the store, buys seven cans of paint and starts painting his flat. After few hours he finishes the whole thing but he realizes that he used only three cans of paint. He calls Ollie:
“Hey man I’ve just finished painting the whole place, but I’ve used only 3 cans of paint and I have 4 left!”
Ollie:
“Yeah, me too.”