foo.cc: In function 'int visit(int, int, int, int)':
foo.cc:18:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 |   for(int i=0;i<ve[begin].size();i++)
      |               ~^~~~~~~~~~~~~~~~~
foo.cc:30:1: warning: no return statement in function returning non-void [-Wreturn-type]
   30 | }
      | ^
foo.cc: At global scope:
foo.cc:31:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   31 | main()
      |      ^

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