foo.cc: In function ‘int main()’:
foo.cc:8:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
    8 |     for(int i=1;i<=st.size()-1;i++)
      |                 ~^~~~~~~~~~~~~