input: Write a function to calculate the maximum possible revenue from the items with given weights and values. The function should take in the list of weights, the list of values, and the number of items, and return the maximum revenue that can be obtained from a knapsack with a given capacity of 5.
  assert knapsack([2, 1, 3], [4, 2, 3], 3)==7
  assert knapsack([1, 2, 3], [1, 4, 3], 3)==7
  assert knapsack([10, 20, 30], [60, 100, 120], 3)==220
  assert knapsack([1, 2], [1, 2], 2)==3
  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]