spacepaste

  1.  
  2. fib(0) = 1
  3. fib(1) = 1
  4. fib(N) = fib_help(1, 1, N - 2)
  5. fib_help(A, B, 0) = A + B
  6. fib_help(A, B, N) = fib_help(B, A + B, N - 1)
  7.