foo.cc: In constructor 'Day::Day(std::string)':
foo.cc:49:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   49 |                 while(index<s.length())
      |                       ~~~~~^~~~~~~~~~~
foo.cc: In member function 'void Persons::print()':
foo.cc:172:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Person*>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  172 |                 for(int i=0;i<v.size();i++)
      |                             ~^~~~~~~~~

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