/in/foo.cc: In function 'int b2ten(int, std::__cxx11::string)':
/in/foo.cc:6:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.size();i++){
              ~^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:18:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<p.size();i++)s=max(s,p[i]-'0');
               ~^~~~~~~~~
/in/foo.cc:19:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<q.size();i++)s=max(s,q[i]-'0');
               ~^~~~~~~~~
/in/foo.cc:20:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<r.size();i++)s=max(s,r[i]-'0');
               ~^~~~~~~~~