foo.cc: In function 'int main()':
foo.cc:12:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~
foo.cc:14:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &vn[i].id, &vn[i].num);
         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:41:13: warning: 'cao' may be used uninitialized in this function [-Wmaybe-uninitialized]
     cout << ansi << endl;
             ^~~~

[Hydro](https://hydro.ac)提供评测服务