Graph Nodes:
X1;X2;X3;X4;X5;X6;X7;X8;X9;X10;X11;X12;X13

Graph Edges:
1. X1 --> X3
2. X1 --> X6
3. X1 --> X9
4. X2 --> X10
5. X2 --> X12
6. X2 --> X13
7. X3 --> X11
8. X3 --> X5
9. X3 --> X7
10. X4 --> X6
11. X5 --> X10
12. X5 --> X6
13. X6 --> X13
14. X6 --> X9
15. X7 --> X8
16. X7 --> X9
17. X8 --> X13
18. X8 --> X9
19. X9 --> X10
20. X9 --> X13

