foo.cc: In function 'int main()':
foo.cc:39:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   39 |     scanf("%d%d%d",&n,&m,&k);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:41:38: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   41 |     for(int i = 1; i <= m; i++) scanf("%d%d%d",&e[i].x, &e[i].y, &e[i].val );
      |                                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务