def _fibin
def _fibout
f fib
    def tmp
    def pov
    = pov 0
    = tmp = _fibin 1
    loop tmp
        = pov 1
        = tmp 0
    .
    = tmp = _fibin 2
    loop tmp
        = pov 1
        = tmp 0
    .
    = tmp - pov 1
    def a
    def b
    = _fibout pov
    loop tmp
        = a - _fibin 1
        = b - a 1
        = _fibin a
        call fib
        = a _fibout
        = _fibin b
        call fib
        = b _fibout
        = tmp 0
        = _fibout + a b
    .
.
inc _fibin
call fib
out _fibout