class Solution:
  def combinationSum(self, candidates, target):
  
    def backtrack(result, index, path, add):
      if add > target:
        return 
        
      if add == target:
        result.append(path[:])
         
      for i in range(index, len(candidates)):

        path.append(candidates[i])
        add += candidates[i]
        backtrack(result, i, path, add)
        add -= candidates[i]
        path.pop()

    result = []
    backtrack(result, 0, [], 0)
     
    return result