(define (fib-helper current target fib-prev fib-now)
                    (if (= current target)
                        fib-now
                        (fib-helper (+ 1 current) target fib-now (+ fib-prev fib-now))))
(define (fib n)
  (if (<= n 2) 1
      (fib-helper 2 n 1 1)))

(fib 7)