sequenceDiagram
Alice->>John: Hello John, how are you?
loop Healthcheck
    John->>John: Fight against hypochondria
end
Note right of John: Rational thoughts!
John-->>Alice: Great!
John->>Bob: How about you?
Bob-->>John: Jolly good!

graph TD
    A[开始] --> B{判断}
    B -- Yes --> C[执行]
    B -- No --> D[跳过]
    C --> E[结束]
    D --> E