Question: I'm trying to do an assignment where I have to find the amount of letters before it gets to a "f" in a string. I was able to get one thing to work, but it only prints out one "f". 

An example of this would be "office", it takes 1 letter to get to one of the "f's", but I can not get it to get to the second f, if that makes sense.

```
a = input()
b = a.index("f")

print(b)

```

Answer: 
Most probably you were doing the following excercise (chapter 2):
<https://github.com/docker/labs/blob/master/beginner/chapters/alpine.md>
and then you moved to the chapter 3.

In addition to King's answer, you should check your default IP.

```
docker-machine ip default 

```
That error looks two interface IP are running thats way your interface getting ambiguity, And its very simply to execute take your docker-machine's ip then hit,

Ex: docker swarm init --advertise-addr 111.111.11.111