static long stupidFib_collab(ICollab collab, int n) {
  ret collab_computeLong(collab,
    receiver -> -> stupidFib_collab(collab, n, receiver));
}

svoid stupidFib_collab(ICollab collab, int n, LongConsumer continuation) {
  if (n < 3) ret with continuation.accept(1L);
  
  var collector = longPairCollector(
    (a, b) -> continuation.accept(a+b));
  
  collab.addWork(-> stupidFib_collab(collab, n-1, collector.setterForA()));
  collab.addWork(-> stupidFib_collab(collab, n-2, collector.setterForB()));
}