foo.cc: In function ‘int main()’:
foo.cc:13:44: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const std::__cxx11::basic_string<char>::size_type’ {aka ‘const long unsigned int’} [-Wsign-compare]
   13 |     while((pos=sentence.find(keyword,pos)) != string::npos)
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~