Find the missing number

Working people frequently ask retired people what they do to make their days interesting.

Well, for example, the other day, Mary my wife and I went into town and visited a shop. We were only in there for about 5 minutes. When we came out, there was a cop writing out a parking ticket.

We went up to him and I said, 'Come on, man, how about giving a senior citizen a break?'
He ignored us and continued writing the ticket. I called him a dumb ass. He glared at me and started writing another ticket for having worn-out tires.
So Mary called him a shit head.  He finished the second ticket and put it on the windshield with the first.
Then he started writing a third ticket.
This went on for about 20 minutes.
The more we abused him, the more tickets he wrote.

Just then our bus arrived, and we got on it and went home. We try to have a little fun each day now that we're retired. It's important at our age.