foo.cc: In function 'void toposort()':
foo.cc:33:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |   for (int i = 0; i < G[tmp].size(); i++)
      |                   ~~^~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:47:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   47 |  scanf("%d", &n);
      |  ~~~~~^~~~~~~~~~
foo.cc:50:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   50 |   scanf("%d",&m);
      |   ~~~~~^~~~~~~~~
foo.cc:56:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   56 |    scanf("%d%d", &a, &b);
      |    ~~~~~^~~~~~~~~~~~~~~~

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