input: Write a function to calculate the maximum possible revenue from items with given weights and values using a dynamic programming approach. The function should take in the list of weights, the list of values, and the number of items, and return the maximum possible revenue achievable with a knapsack of capacity 5.
  assert knapsack([2, 1, 3], [4, 2, 3], 3)==7
  assert knapsack([3, 2, 1], [5, 3, 4], 3)==9
  assert knapsack([1, 2, 3], [1, 2, 3], 3)==5
  assert knapsack([1, 1, 1], [10, 20, 30], 3)==50
  assert knapsack([], [], 0)==0
output: def knapsack(weights, values, n):
      capacity = 5
      dp = [0] * (capacity + 1)
      
      for i in range(n):
          for w in range(capacity, weights[i] - 1, -1):
              dp[w] = max(dp[w], dp[w - weights[i]] + values[i])
      
      return dp[capacity]