foo.cc: In function 'int main()':
foo.cc:30:19: 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(len=1;len<=s.size();len++)
      |                ~~~^~~~~~~~~~
foo.cc:33:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   33 |         for(i=0;i<s.size();++i)
      |                 ~^~~~~~~~~
foo.cc:35:13: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   35 |         if(i>=s.size()) break;
      |            ~^~~~~~~~~~

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