title: finding the greatest Fibonacci number within limited time in python
body: <p>I need a code that calculates nth fibonacci number as well as giving me the time used to calculate it, in python.</p>
  
  <pre><code>def fib(n):
      if n==0 or n==1: return 1
      else: return fib(n-1)+fib(n-2)
  </code></pre>
  
  <p>The calculation of the number step must use a such method.</p>