fib =: monad : 0 M. NB. M. means that it is memoized
if. 1>:y do.
	x: 1
else.
	(fib y-1)+fib y-2
end.
)

fibs =: ; fib each i.50 NB. first 50 should be enough lol

problem2 =: +/((0=2|fibs)*.(fibs<4000000))#fibs