The love of functions and derivatives

That night Derivative was blown by the wind outside the corridor for 15 minutes. When he returned to the ward, Function was already asleep. Derivative tucked up the quilt for him. He was about to lift his feet and was about to leave. Derivative abruptly withdrew his steps and took care of Function. Smoothing the broken hair on his forehead, he let out a faint sigh.

The following night, the two of them had a tacit understanding and did not mention this matter.

Time flies, one month has passed, and it is time for the function to be discharged from the hospital. It was originally agreed that the derivative will pick up the function tonight, but the function suddenly wants to be discharged early.

He wanted to give Derivative a surprise, and put aside some of his own thoughts. Anyway, he worked so hard to take care of himself for a month every night like clocking in at work, and he had to prepare some gifts to express his gratitude.

Function was discharged from the hospital at noon. It took him an afternoon to browse the surrounding shopping malls before he picked out a tie that he was satisfied with.

At about 06:30 in the evening when I got off work, Function took a taxi to the office building.The old man at the door also asked about the current physical condition of the function, and the function was flattered and said that he was almost recovered.

On the way, I met a lot of colleagues asking about their health. Function was anxious to see the derivative, so he replied to everyone in a simple and polite manner, and strode towards the office building where the derivative worked, walking like flying.

It was only at the bottom of the building that the function's phone rang.

"I can't come tonight. I'm really sorry. If you don't mind, I'll pick you up tomorrow night." Derivative's voice sounded urgent, "Anyway, you should have a good rest."

A good rest is usually the end of a phone call, the function is aware of this, and hurriedly asks before the derivative hangs up, "What's the matter?"

The other party paused for a second before saying, "I need to process some documents, and I need to work overtime tonight."

The function is standing downstairs in the derivative office. Most of the mathematical definitions are home. Only a few office windows are lit. In fact, the function clearly knows that the derivative office is the fifth window on the sixth floor, but the function is from the first floor. Counting to the sixth floor, counting from the first window to the fifth window, counting three times, each time the result is the same——

The lights in the derivative office were off.

What if the derivative is going to hand over work, so he is not in the office for the time being?

Obviously he could take the elevator, Function slowly climbed up the stairs, and when he arrived at the derivative office, the door of the office was locked.

Probability just came out of the bathroom and saw that Function is now next door to his office—Derivative's office, "I heard that you have been recuperating in the hospital for a month? What happened? Your injury is already healed?"

Function had no intention of chatting with probability, and only vaguely said that he had an operation for his heart injury, and now he can be discharged from the hospital. Function did not forget the purpose of his trip, so he asked probability: "Have you seen the derivative?"

"He's off work, and he left work early on purpose today." Probabilities shook his head and sighed, "Big boss is worthy of being a big boss. He actually dared to leave early, even 10 minutes early. I wouldn't dare to ask for it."

"Are you looking for derivatives?" Probability asked curiously.

"It's not a big deal." The function looked back at the door of the derivative office, and the bag with the tie in its hand was as heavy as it was. The function turned around and said without looking back, "I still have something to do, I'll go first gone."