class Solution:
  def countSubsets(self, num, s):
    def dp(index, acc, memo):
      
      if (index, acc) in memo:
        return memo[(index, acc)]

      if acc == s:
        return 1

      if index == len(num):
        return 0 

      result = dp(index + 1, acc, memo) + dp(index + 1, acc + num[index], memo)
      memo[(index, acc)] = result

      return result
      
    return dp(0, 0, {})