## 题目描述

You are considering renting a moving truck to help you move from Waterloo to the big city. Gas prices being so high these days, you want to know how much the gas for this beast will set you back.

The truck consumes a full liter of gas for each kilometer it travels. It has a 200-liter gas tank. When you rent the truck in Waterloo, the tank is half-full. When you return it in the big city, the tank must be at least half-full, or you'll get gouged even more for gas by the rental company. You would like to spend as little as possible on gas, but you don't want to run out along the way.

## 输入

The input begins with a single positive integer on a line by itself indicating the number of test cases, followed by a blank line.

Each test case is composed only of integers. The first integer is the distance in kilometers from Waterloo to the big city, at most 10,000. Next comes a set of up to 100 gas station specifications, describing all the gas stations along your route, in non-decreasing order by distance. Each specification consists of the distance in kilometers of the gas station from Waterloo, and the price of a liter of gas at the gas station, in tenths of a cent, at most 2,000.

There is a blank line between each two consecutive inputs.

## 输出

For each test case, output the minimum amount of money that you can spend on gas to get from Waterloo to the big city. If it is not possible to get from Waterloo to the big city subject to the constraints above, print “Impossible''.

The output of each two consecutive cases will be separated by a blank line.

## 样例输入

```
1
500
100 999
150 888
200 777
300 999
400 1009
450 1019
500 1399
```

## 样例输出

```
450550
```

## 参考代码

```
暂无
```

## 解析

暂无