foo.c: In function 'main':
foo.c:9:9: error: 'i' undeclared (first use in this function)
foo.c:9:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:17:15: error: 'ans' undeclared (first use in this function)
foo.c:32:1: warning: control reaches end of non-void function [-Wreturn-type]