/in/foo.cc:13:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:19:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
                   ^
/in/foo.cc:21:94: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%s %d %d %c %c %d",stu[i].a,&stu[i].b,&stu[i].c,&stu[i].d,&stu[i].e,&stu[i].f);
                                                                                              ^