add edges
Add_edge ( 1 , 2 ) NEW_LINE Add_edge ( 1 , 3 ) NEW_LINE Add_edge ( 1 , 4 ) NEW_LINE Add_edge ( 3 , 5 ) NEW_LINE Add_edge ( 3 , 7 ) NEW_LINE Add_edge ( 5 , 6 ) NEW_LINE Add_edge ( 5 , 8 ) NEW_LINE Add_edge ( 7 , 9 ) NEW_LINE intisalise ( ) NEW_LINE