/in/foo.cc: In function 'int main()':
/in/foo.cc:11:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<a.size();j++)
               ~^~~~~~~~~
/in/foo.cc:12:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int t=0;t<b.size();t++)
                ~^~~~~~~~~