/in/foo.cc: In function 'bool check(std::__cxx11::string)':
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<str.size();i++)
              ~^~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:26:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<st.size();i++)
              ~^~~~~~~~~~
/in/foo.cc:31:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if(i==st.size()-1&&check(s))
       ~^~~~~~~~~~~~~