Euler Project problems in C

To practice writing C, I started doing some Euler project problems. Two notes:

1. Spoilers. If you're doing them yourself, be warned.
2. I'm sure this is awful, non-idiomatic C. I'm self-taught!

That's it! I mostly did this on a flight so I didn't get super far and I'm really just putting this on GitHub to have a second copy.

To build one:

$ ./build.sh
USAGE: ./build.sh <exercise-to-compile>
$ ./build.sh 1-3-and-5.c
$ ./build/1-3-and-5