(*
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

Find the sum of all the even-valued terms in the sequence which do not exceed four million.
*)

let sumup =
  let rec sumup i j s =
    if (i>4000000) then s else
    ( sumup j (i+j)
	( if (i mod 2 = 0) then (s+i) else s ) )
  in
    sumup 1 2 0
;;

Printf.printf "%d\n" (sumup);;