(*
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

Find the sum of all the primes below two million.
*)

open Big_int;;

let sumofprimes =
  let rec sumup x ps s =
    if( x mod 100 = 0) then (Printf.printf "%d\n" x) else ();
    if (x>2000000) then s else
    if (List.exists (fun y -> (x mod y=0) ) ps)
    then sumup (x+1) ps s
    else sumup (x+1) (x::ps) (add_int_big_int x s)
  in
    sumup 2 [] (big_int_of_int 0)
;;

Printf.printf "%s\n" (string_of_big_int sumofprimes);;