/in/foo.cc: In function 'void bfs()':
/in/foo.cc:50:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     for(int j=t.s.find(a[i]);j>=0&&j<=(t.s.length()-a[i].length());j=t.s.find(a[i],j+1))
                                                    ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~