foo.cc: In function 'int main()':
foo.cc:7:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |         for (int i = 0; i < a.size(); i++)
      |                         ~~^~~~~~~~~~
foo.cc:10:35: 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 j = 0; j < b.size(); j++)
      |                                 ~~^~~~~~~~~~
foo.cc:21:43: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 |                         for (int k = 0; k < c.size(); k++) cout << c[k];
      |                                         ~~^~~~~~~~~~

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