ILL 1983 Problem 45

Let two glasses, numbered $1$ and $2$ , contain an equal quantity of liquid, milk in glass $1$ and coffee in glass $2$ . One does the following: Take one spoon of mixture from glass $1$ and pour it into glass $2$ , and then take the same spoon of the new mixture from glass $2$ and pour it back into the first glass. What happens after this operation is repeated $n$ times, and what as $n$ tends to infinity?