digraph G {
  1;
  2;
  3;
  4;
  5;
  
  
  1 -> 2 [label="0", ];
  2 -> 3 [label="0", ];
  2 -> 5 [label="0", ];
  3 -> 4 [label="0", ];
  4 -> 5 [label="0", ];
  
  }