/in/foo.cc: In function 'int main()':
/in/foo.cc:11:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         if(i==a.size())break;
            ~^~~~~~~~~~
/in/foo.cc:14:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     while(i<a.size()){
           ~^~~~~~~~~
/in/foo.cc:16:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(i==a.size())break;
                ~^~~~~~~~~~
/in/foo.cc:20:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             if(i==a.size())break;
                ~^~~~~~~~~~