            let hantei a b = if (a + b) mod 3 = 0 then "Possible"
            else if a mod 3 = 0 then "Possible"
            else if b mod 3 = 0 then "Possible"
            else "Impossible"
             
            let main () =
            let kekka = hantei a b ;;
            print_string kekka;;
             
            let () = main ()