/in/foo.cc: In function 'int main()':
/in/foo.cc:27:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                    for(int j=0;j<a[i].size();j++)
                                ~^~~~~~~~~~~~
/in/foo.cc:41:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                    for(int j=2;j<a[i].size();j++)
                                ~^~~~~~~~~~~~