foo.cc: In function ‘int main()’:
foo.cc:15:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   15 |                 for(int i=0;i<s.size()-2;i++)
      |                             ~^~~~~~~~~~~
foo.cc:21:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   21 |                 for(int i=0;i<s.size()-3;i++)
      |                             ~^~~~~~~~~~~
foo.cc:24:14: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   24 |         if(ok=0)
      |            ~~^~