Graph Nodes:
X1;X2;X3;X4;X5;X6;X7;X8;X9;X10;X11;X12;X13;X14;X15;X16;X17;X18;X19;X20

Graph Edges:
1. X1 --> X13
2. X1 --> X3
3. X1 --> X4
4. X1 --> X8
5. X10 --> X12
6. X10 --> X16
7. X11 --> X14
8. X11 --> X15
9. X12 --> X15
10. X15 --> X19
11. X16 --> X20
12. X2 --> X13
13. X2 --> X20
14. X2 --> X3
15. X3 --> X10
16. X3 --> X20
17. X3 --> X6
18. X3 --> X9
19. X4 --> X14
20. X4 --> X15
21. X4 --> X5
22. X4 --> X6
23. X5 --> X20
24. X5 --> X7
25. X6 --> X7
26. X7 --> X14
27. X8 --> X14
28. X8 --> X18
29. X8 --> X19
30. X8 --> X9

