Graph Nodes:
X1;X2;X3;X4;X5;X6;X7;X8

Graph Edges:
1. X1 --> X2
2. X2 --> X6
3. X3 --> X4
4. X3 --> X5
5. X4 --> X6
6. X5 --> X8
7. X6 --> X7
8. X6 --> X8
