create undirected edges initialize the tree given in the diagram
v [ 1 ] . push ( 2 ) ; v [ 2 ] . push ( 1 ) ; v [ 1 ] . push ( 3 ) ; v [ 3 ] . push ( 1 ) ; v [ 1 ] . push ( 4 ) ; v [ 4 ] . push ( 1 ) ; v [ 2 ] . push ( 5 ) ; v [ 5 ] . push ( 2 ) ; v [ 2 ] . push ( 6 ) ; v [ 6 ] . push ( 2 ) ; v [ 3 ] . push ( 7 ) ; v [ 7 ] . push ( 3 ) ; v [ 4 ] . push ( 8 ) ; v [ 8 ] . push ( 4 ) ; v [ 4 ] . push ( 9 ) ; v [ 9 ] . push ( 4 ) ; v [ 4 ] . push ( 10 ) ; v [ 10 ] . push ( 4 ) ; v [ 5 ] . push ( 11 ) ; v [ 11 ] . push ( 5 ) ; v [ 5 ] . push ( 12 ) ; v [ 12 ] . push ( 5 ) ; v [ 7 ] . push ( 13 ) ; v [ 13 ] . push ( 7 ) ; v [ 7 ] . push ( 14 ) ; v [ 14 ] . push ( 7 ) ;