/in/foo.cc: In function 'int main()':
/in/foo.cc:12:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |                 for (int len=2;len<=s.size()-2;len++)
      |                                ~~~^~~~~~~~~~~~
/in/foo.cc:13:48: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |                         for(int l=0,r=l+len-1;r<s.size()-2;l++,r++)
      |                                               ~^~~~~~~~~~~