foo.cc: In function 'std::string ex(std::string)':
foo.cc:10:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |  for (int i=0; i<s.length(); i++)
      |                ~^~~~~~~~~~~
foo.cc: In function 'void maxChar(std::string)':
foo.cc:24:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |  for (i = 0; i < s.length() ; i+=2)
      |              ~~^~~~~~~~~~~~
foo.cc:30:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |  for (i = 0; i < s.length() ; i+=5)
      |              ~~^~~~~~~~~~~~

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