/in/foo.c: In function 'f':
/in/foo.c:12:9: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return j;
         ^
/in/foo.c: In function 'main':
/in/foo.c:27:8: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
   a1=a1/t;
      ~~^~