/in/foo.c: In function 'main':
/in/foo.c:19:29: error: 'next' undeclared (first use in this function); did you mean 'nxet'?
   19 |                 printf("%d",next);
      |                             ^~~~
      |                             nxet
/in/foo.c:19:29: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:18:21: warning: unused variable 'nxet' [-Wunused-variable]
   18 |                 int nxet=f0+f1;
      |                     ^~~~