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 --> X19
2. X1 --- X2
3. X1 --- X6
4. X1 --- X9
5. X10 --> X20
6. X11 --- X14
7. X11 --> X18
8. X13 --> X20
9. X14 --> X18
10. X18 --> X20
11. X2 --- X10
12. X2 --- X6
13. X3 --- X11
14. X3 --- X4
15. X3 --- X8
16. X4 --> X19
17. X5 --> X12
18. X5 --- X13
19. X5 --> X16
20. X6 --- X10
21. X7 --> X12
22. X7 --> X18
23. X8 --> X16
24. X8 --- X17
25. X8 --> X18
26. X9 --- X15
27. X9 --> X16

