input: Write a Python function that identifies three elements, one from each of three sorted lists, such that the maximum difference between these elements is minimized.
  assert find_closet([1, 4, 10],[2, 15, 20],[10, 12],3,3,2) == (10, 15, 10)
  assert find_closet([20, 24, 100],[2, 19, 22, 79, 800],[10, 12, 23, 24, 119],3,5,5) == (24, 22, 23)
  assert find_closet([2, 5, 11],[3, 16, 21],[11, 13],3,3,2) == (11, 16, 11)
output: def find_closet(A, B, C, p, q, r):
      i, j, k = 0, 0, 0
      diff = float('inf')
      res_i, res_j, res_k = 0, 0, 0
      while i < p and j < q and k < r:
          maximum = max(A[i], B[j], C[k])
          minimum = min(A[i], B[j], C[k])
          if diff > (maximum - minimum):
              diff = maximum - minimum
              res_i, res_j, res_k = A[i], B[j], C[k]
          if minimum == A[i]:
              i += 1
          elif minimum == B[j]:
              j += 1
          else:
              k += 1
      return res_i, res_j, res_k