foo.cc: In function 'int main()':
foo.cc:30:15: 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(int i=0;i<=s1.size()-1;i++)
      |              ~^~~~~~~~~~~~~
foo.cc:35:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   35 |  for(int i=0;i<=s1.size()-1;i++)
      |              ~^~~~~~~~~~~~~

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