# Integer chemistry III

**Computer Science**Level 4

\[ 6 = 1+1+1+1+1+1 \\ = (1+1)*(1+1)+1+1 \\ = (1+1)*(1+1+1) \]

We say the number 6 has complexity 5, because that's the cheapest (using the fewest ones) way it can be built. The allowed operations are addition, multiplication and brackets. It's not allowed to write two ones next to each other to make 11.

What's the smallest number with complexity 13?

This is the final problem in a series of 3. You are encouraged to solve the previous problems first.