// VertexImplications: if v is in the cover and (v,w) is an implication,
// then w must also be in the cover.
// forbidden(w): exists v with (v,w) in I and G[v]=1 and G[w]=0.
// advance: G[w] := 1.

class VertexImplications {
  void VertexImplications(int[][] I, boolean[] G) {
    forbidden (w) :
      exists v in [0..n-1] : I[v][w] == 1 && G[v] && !G[w]
    =>
      advance : G[w] = true;
  }
}