# The Road to Berland is Paved With Good Intentions

## 输入输出格式

### 输入格式

The first line contains two space-separated integers \$ n,m \$ ![](https://cdn.luogu.com.cn/upload/vjudge_pic/CF228E/ee7c96350f329f0ac22650cf104d480a00efba5a.png) — the number of cities and roads in Berland, correspondingly. Next \$ m \$ lines contain the descriptions of roads in Berland: the \$ i \$ -th line contains three space-separated integers \$ a_{i},b_{i},c_{i} \$ \$ (1<=a_{i},b_{i}<=n; a_{i}≠b_{i}; 0<=c_{i}<=1) \$ . The first two integers \$ (a_{i},b_{i}) \$ are indexes of the cities that are connected by the \$ i \$ -th road, the third integer \$ (c_{i}) \$ equals 1, if the road was initially asphalted, and 0 otherwise. Consider the cities in Berland indexed from 1 to \$ n \$ , and the roads indexed from 1 to \$ m \$ . It is guaranteed that between two Berlandian cities there is not more than one road.

### 输出格式

In the first line print a single integer \$ x \$ \$ (0<=x<=n) \$ — the number of days needed to asphalt all roads. In the second line print \$ x \$ space-separated integers — the indexes of the cities to send the workers to. Print the cities in the order, in which Valera send the workers to asphalt roads. If there are multiple solutions, print any of them. If there's no way to asphalt all roads, print "Impossible" (without the quotes).

## 输入输出样例

### 输入样例 #1

``````4 4
1 2 1
2 4 0
4 3 1
3 2 0
``````

### 输出样例 #1

``````4
3 2 1 3
``````

### 输入样例 #2

``````3 3
1 2 0
2 3 0
3 1 0
``````

### 输出样例 #2

``````Impossible
``````