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

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

