input: 
  def knapsack(weights: List[int], values: List[int], n: int) -> int:
      """Calculate the maximum possible revenue from the items with given weights and values.
      
      >>> knapsack([2, 1, 3], [4, 2, 3], 3)
      7
      >>> knapsack([1, 2, 3], [6, 10, 12], 3)
      22
      """
      
      # total capacity of knapsack 
      W = 5
      
      # matrix to store solution matrix 
      K = [[0 for x in range(W+1)] for x in range(n+1)] 
      
      # build the solution matrix in bottom up manner 
      for i in range(n+1): 
          for w in range(W+1): 
              if i==0 or w==0: 
                  K[i][w] = 0
              elif weights[i-1] <= w: 
                  K[i][w] = max(values[i-1] + K[i-1][w-weights[i-1]],  K[i-1][w]) 
              else: 
                  K[i][w] = K[i-1][w] 
      
      return K[n][W]
  
output:     return K[n][W]