Little help for everybody who struggles with "a" and "an":

If the next word starts with a consonant (b, c, d, ect.) it's mostly "a" (except words like "hour" where the consonant is silent. In this case, it's "an").
If the next word starts with a vocal (a, e, i, o, u) it's always "an".

Why?
Well, try to say "a igloo" as fast as you can. It's some kind of a tongue-twister, isn't it?
Now try the same with "an igloo". Much easier, right?
The same with "an nice igloo". Pretty difficulty, huh?
Try "a nice igloo". Easier.

Have a nice day^^