I can't compile this. What am I doing wrong? Here is the output:

$ gcc -o donut donut.c -lm

donut.c:1: warning: data definition has no type or storage class

donut.c: In function ‘main’:

donut.c:4: warning: incompatible implicit declaration of built-in function ‘printf’

donut.c:5: warning: incompatible implicit declaration of built-in function ‘memset’