Desigining the tree
adj [ 1 ] . push_back ( 2 ) ; adj [ 2 ] . push_back ( 1 ) ; adj [ 1 ] . push_back ( 3 ) ; adj [ 3 ] . push_back ( 1 ) ; adj [ 2 ] . push_back ( 4 ) ; adj [ 4 ] . push_back ( 2 ) ; adj [ 2 ] . push_back ( 5 ) ; adj [ 5 ] . push_back ( 2 ) ; adj [ 3 ] . push_back ( 6 ) ; adj [ 6 ] . push_back ( 3 ) ; adj [ 3 ] . push_back ( 7 ) ; adj [ 7 ] . push_back ( 3 ) ;