/in/foo.cc: In function 'int main()':
/in/foo.cc:22:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (i=0;i<in.size();i++){
              ~^~~~~~~~~~
/in/foo.cc:16:11: warning: unused variable 'n' [-Wunused-variable]
     int i,n;
           ^