// Fast connected components: SlowComponents accelerated by a
// pointer-jumping clause G[j] >= G[G[j]], which doubles the effective
// reach of the label-propagation step at each round and brings the
// number of rounds down from O(diameter) to O(log diameter).

class FastComponents {
  int[] FastComponents(set<int>[] adj) {
    int[]      G = _i;
    ensure (j) : G[j] >= G[G[j]];
    ensure (j) : G[j] >= max i in adj[j] : G[i];
    return G;
  }
}