Postage Stamp Problem with 3 stamp types > The Baker does not sell individual bear claws, but sells them in boxes of 6, 9, and 20. Assuming an unlimited supply, what is the largest number of bear claws that I cannot buy from the baker. I'm not sure how to attack one of these problems when given three types.

**Hint:** You can buy $n$ bear claws, where $n \in N =\\{6a+9b+20c \,| a,b,c \in \Bbb{N}\\} $.

Let $M = \\{m|m \in \Bbb N \wedge m \
otin N\\}$.

You want $\sup M$.

Notice that if $b,c = 0$, every sixth number is in $N$. This implies that if six consecutive numbers are in $N$, all numbers greater than those will also be in $N$.