Stores the Tree
var tr = Array . from ( Array ( n + 1 ) , ( ) => Array ( ) ) ; tr [ 0 ] . push ( 3 ) ; tr [ 0 ] . push ( 4 ) ; tr [ 4 ] . push ( 6 ) ; tr [ 6 ] . push ( 2 ) ; tr [ 2 ] . push ( 1 ) ; tr [ 2 ] . push ( 8 ) ; tr [ 8 ] . push ( 5 ) ; tr [ 5 ] . push ( 7 ) ;