PROGRAMMING:How Long Does It Take

Given the relations of all the activities of a project, you are supposed to find the earliest completion time of the project.
### Input Specification:
Each input file contains one test case. Each case starts with a line containing two positive integers $$N$$ ($$\le 100$$), the number of activity check points (hence it is assumed that the check points are numbered from 0 to $$N-1$$), and $$M$$, the number of activities. Then $$M$$ lines follow, each gives the description of an activity. For the `i`-th activity, three non-negative numbers are given: `S[i]`, `E[i]`, and `L[i]`, where `S[i]` is the index of the starting check point, `E[i]` of the ending check point, and `L[i]` the lasting time of the activity. The numbers in a line are separated by a space.
### Output Specification:
For each test case, if the scheduling is possible, print in a line its earliest completion time; or simply output "Impossible".
### Sample Input 1:
```in
9 12
0 1 6
0 2 4
0 3 5
1 4 1
2 4 1
3 5 2
5 4 0
4 6 9
4 7 7
5 7 4
6 8 2
7 8 4
```
### Sample Output 1:
```out
eighteen
```
### Sample Input 2:
```
4 5
0 1 1
0 2 2
2 1 3
1 3 4
3 2 5
```
### Sample Output 2:
```
Impossible
```






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