/in/foo.c: In function 'main':
/in/foo.c:20:33: error: invalid type argument of '->' (have 'student {aka struct stu}')
   scanf("%s %d %d %c %c %d",&stu->name,&stu.avg,&stu.vi,&stu.ganbu,&stu.xibu,&stu.lunwen);
                                 ^~
/in/foo.c:42:26: error: invalid type argument of '->' (have 'student {aka struct stu}')
  printf("%s\n%d\n%d",flag->name,flag.all,sum);
                          ^~