let is_rel_prime x ps =
        not ( List.exists ( fun y -> x mod y = 0 ) ps )
;;

let rec is_truncable_left x ps =
        (x=0) ||
        ((List.mem x ps) && (is_truncable_left (x/10) ps))
;;

let digits x =
        let rec digits d =
                if( 10*d > x )
                then d
                else digits (10*d)
        in
                digits 1
;;

let is_truncable_right x ps =
        let rec is_truncable_right x d =
                if( x=0 ) then true else
                if( List.mem x ps )
                then is_truncable_right (x mod d) (d/10)
                else false
        in
                is_truncable_right x (digits x)
;;

let is_truncable x ps =
        (is_truncable_left x ps) &&
        (is_truncable_right x ps)
;;

let search =
        let rec search x ps n s =
                Printf.printf "%d\n" x;
                if( n = 11 ) then (Printf.printf "sum=%d\n" s) else
                if( is_rel_prime x ps )
                then
                        if( is_truncable x (x::ps) )
                        then (
                                Printf.printf "%d\n" x;
                                search (x+2) (x::ps) (n+1) (s+x)
                        ) else search (x+2) (x::ps) n s
                else
                        search (x+2) ps n s

        in
                search 11 [2;3;5;7] 0 0