foo.cc: In function 'int main()':
foo.cc:16:38: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |                         for(int i=1;i<a.length();i++){
      |                                     ~^~~~~~~~~~~
foo.cc:42:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |                         for(;i<a.length();i++){
      |                              ~^~~~~~~~~~~

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