foo.cc: In function 'int main()':
foo.cc:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
foo.cc:29:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&i);
   ~~~~~^~~~~~~~~
foo.cc:30:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",w+i,&son);
         ~~~~~^~~~~~~~~~~~~~~~~
foo.cc:31:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         while (son--){++t[s]; scanf("%d",&s); addedge(i,s);}
                               ~~~~~^~~~~~~~~

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