若x，y满足约束条件 $\{\begin{array}{l}x-y+1\ge 0\\ x+y-3\ge 0\\ x-3\le 0\end{array}$ ，则z=x﹣2y的最小值为____．

Characters: Peppa, George, Mummy Pig, Daddy Pig

Setting: Mummy Pig is working on her computer. Daddy Pig is making soup for lunch.

Peppa: Daddy? Can we go and watch mummy on her computer?

Daddy Pig: Yes, as long as you don't disturb her. She has a lot of important work to do today.

Peppa: Thank you, Daddy!

Peppa: (Peppa and George run into mummy's room.) Mummy. Can George and I sit on your legs and watch you work?

Mummy Pig: Yes, if you both sit quietly.

Peppa: (Peppa and George watch mummy work on the computer for a while.) Mummy? Can we play that computer game Happy Mrs. Chicken?

Mummy Pig: We can play Happy Mrs. Chicken later. But now I have to work.

Peppa: Mummy? Can we help you work?

Mummy Pig: No, Peppa! You mustn't touch the computer. And George, you mustn't touch the computer, either.

Peppa: Yes, George. You mustn't do this (Peppa began to knock on the keyboard).

Mummy Pig: Peppa, stop!

Peppa: Sorry, Mummy. I was just showing George what not to do.

Mummy Pig: Oh, dear. The computer doesn't work!

    More than 95 percent of people in the world have phones today, according to the United Nations. People use phones to make phone calls and send ____ (信息)to communicate with others. Now we hardly write letters. But a TV show, Letters Alive, is bringing back this old ____(习惯).

    Letters Alive gets its idea from a UK program with a ____ (相似的) name. They have something in common. The shows both ____ (邀请) famous actors and actresses, but there are no funny jokes or different competitions.____ (代替), it is just one person reading a letter. Since it has been on in____ (十二月) , Letters Alive has been widely praised.

    The letters were written by people from different times in history. For example, once they read a letter written by famous writer Xiao Hong to her brother who is ____ (年轻的) than her in 1941. The letter shows that Xiao Hong____ (想念) her brother so much and had great hopes for his future.

    “Every letter opens another world for us,” said Guan Zhengwen, the ____ (导演) of the TV show. “It seems that we can experience the real lives and feelings of the writers.”

____ (不管怎么说)，many people said that it has provided a breath of fresh air to today's TV shows.