foo.cc: In function 'int main()':
foo.cc:8:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    8 | for (int i=1; i<=s1.length(); i++)
      |               ~^~~~~~~~~~~~~
foo.cc:9:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    9 | for (int j=1; j<=s2.length(); j++)
      |               ~^~~~~~~~~~~~~

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