let rec fib n : int =
  if n <= 0 then 0
  else if n = 1 then 1
  else fib (n-1) + fib (n-2)

let rec sum_even_fib n =
  let fib_n =
    fib n
  in
  if fib_n > 4000000 then 0
  else if fib_n mod 2 != 0 then sum_even_fib (n+1)
  else fib_n + sum_even_fib (n+1)

let _ =
  print_int (sum_even_fib 1);
  print_newline ();

let rec fib n : int =
  if n <= 0 then 0
  else if n = 1 then 1
  else fib (n-1) + fib (n-2)

let rec sum_even_fib n =
  let fib_n =
    fib n
  in
  if fib_n > 4000000 then 0
  else if fib_n mod 2 != 0 then sum_even_fib (n+1)
  else fib_n + sum_even_fib (n+1)

let _ =
  print_int (sum_even_fib 1);
  print_newline ();