/in/foo.cc: In function 'int main()':
/in/foo.cc:7:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=n.size();i++){
              ~^~~~~~~~~~
/in/foo.cc:12:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<n.size();i++){
              ~^~~~~~~~~