-module euler2 -export find_sum find_sum when if rem find_sum true fin

-module(euler2).
-export([find_sum/1]).

find_sum(S, A, B, N) when A<N ->
    if 
        A rem 2 == 0 -> 
	    find_sum(S+A, B, A+B, N);
	true -> find_sum(S, B, A+B, N)
    end;
find_sum(S, A, _, N) when A>=N ->
    S.

find_sum(N) ->
  find_sum(0, 1, 2, N).