input: 
  def max_revenue(prices):
      """ Calculate the maximum revenue that can be made from buying and selling stocks on different days.
      The prices list represents the price of a stock on each day. The function calculates the maximum profit
      by finding the maximum difference between buying and selling on different days.
      >>> max_revenue([10, 7, 5, 8, 11, 9])
      6
      """
      diff = [prices[i + 1] - prices[i] for i in range(len(prices) - 1)] 
      max_diff = 0
      for i in range(len(diff)): 
          for j in range(i + 1, len(diff) + 1): 
              current_diff = sum(diff[i:j]) 
              if current_diff > max_diff: 
                  max_diff = current_diff 
   
      return max_diff
  
output:     min_price = prices[0]
      max_profit = 0
      for price in prices:
          if price < min_price:
              min_price = price
          elif price - min_price > max_profit:
              max_profit = price - min_price
      return max_profit