How can we know the order of a Feynman diagram just from the pictorial representation?

Is it the number of vertices divided by 2?

For example, I know that electnro-positron annihilaiton is first order:
![enter image description here](https://i.stack.imgur.com/vB1sH.png)

So what's the order of, for instance, a radiative penguin diagram (below) ?

![enter image description here](https://i.stack.imgur.com/DiZZY.png)