/in/foo.cc: In function 'bool check(std::string)':
/in/foo.cc:10:30: warning: left operand of comma operator has no effect [-Wunused-value]
   10 |         for(int i=0,j=len/2;i<len/2,j<len;i++,j++)
      |                             ~^~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:24:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |                 for(int i=0;i<s.size()-3;i++)
      |                             ~^~~~~~~~~~~
/in/foo.cc:26:40: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |                         for(int j=i+1;j<s.size()-2;j+=2)
      |                                       ~^~~~~~~~~~~
/in/foo.cc:29:48: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |                                 for(int l=k+1;l<s.size();l+=2)
      |                                               ~^~~~~~~~~