Let **S1** and **S2** be two stacks. **S1** has capacity of 4 elements. **S2** has capacity of 2 elements. **S1** already has 4 elements: 100, 200, 300, and 400, whereas **S2** is empty, as shown below.

Stack S1 |
---|

400 (Top) |

300 |

200 |

100 |

Stack S2 |
---|

Only the following three operations are available:

**PushToS2:** Pop the top element from **S1** and push it on **S2**.**PushToS1:** Pop the top element from **S2** and push it on **S1**.**GenerateOutput:** Pop the top element from **S1** and output it to the user.

Note that the pop operation is not allowed on an empty stack and the push operation is not allowed on a full stack.

Which of the following output sequences can be generated by using the above operations?

Consider the following sequence of operations on an empty stack.

push(54); push(52); pop(); push(55); push(62); s = pop();

Consider the following sequence of operations on an empty queue.

enqueue(21); enqueue(24); dequeue(); enqueue(28); enqueue(32); q = dequeue();

The value of s + q is ______