Stores the Tree
vector < vector < int > > tr ( n + 1 ) ; tr [ 0 ] . push_back ( 3 ) ; tr [ 0 ] . push_back ( 4 ) ; tr [ 4 ] . push_back ( 6 ) ; tr [ 6 ] . push_back ( 2 ) ; tr [ 2 ] . push_back ( 1 ) ; tr [ 2 ] . push_back ( 8 ) ; tr [ 8 ] . push_back ( 5 ) ; tr [ 5 ] . push_back ( 7 ) ;