apollo:~ craig$ clang -std=c11 -o main main.c
apollo:~ craig$ time ./main
36

real	0m11.446s
user	0m11.437s
sys	0m0.005s

apollo:~ craig$ clang -std=c11 -O3 -o main main.c
apollo:~ craig$ time ./main
36

real	0m4.229s
user	0m4.222s
sys	0m0.004s