diff --git a/harald/api.py b/harald/api.py
index b879417..4fd7044 100644
--- a/harald/api.py
+++ b/harald/api.py
@@ -21,9 +21,7 @@ class APIError(Exception):
 
 
 def select(problem: str):
-    response = requests.post(
-        config.contest_url + "/select", json={"problemName": problem, "id": config.id}
-    )
+    response = requests.post(config.contest_url + "/select", json={"problemName": problem, "id": config.id})
     if not response.ok:
         raise APIError(f"{response.status_code}: {response.text}")
 
@@ -77,8 +75,7 @@ def explore(plans: List[str]):
 
 
 def guess(layout):
-    data = {"id": config.id, "map": layout}  # , "id": config.id}
-    print(json.dumps(data))
+    data = {"map": layout, "id": config.id}
     response = requests.post(config.contest_url + "/guess", json=data)
     if not response.ok:
         raise APIError(f"{response.status_code}: {response.text}")
diff --git a/harald/explore.py b/harald/explore.py
index 29e6ac0..0be60e8 100755
--- a/harald/explore.py
+++ b/harald/explore.py
@@ -140,9 +140,7 @@ class Explore:
                 # self.dump()
 
                 p, rid = self.neighbors[pl][d]
-                assert (
-                    rid is None or rid == room_id
-                ), f"penultimate {path} {pl}: {rid} != {room_id}"
+                assert rid is None or rid == room_id, f"penultimate {path} {pl}: {rid} != {room_id}"
                 self.neighbors[pl][d] = (p, room_id)
 
                 # self.dump()
@@ -185,9 +183,7 @@ class Explore:
         assert path2 in self.rooms, f"room '{path2}' not explored"
 
         if self.rooms[path1] != self.rooms[path2]:
-            raise ExploreError(
-                f"ids of '{path1}'({self.rooms[path1]}) and '{path2}'({self.rooms[path2]}) do not match"
-            )
+            raise ExploreError(f"ids of '{path1}'({self.rooms[path1]}) and '{path2}'({self.rooms[path2]}) do not match")
 
         path = min(path1, path2)
         pmerge = max(path1, path2)
@@ -196,13 +192,9 @@ class Explore:
         self.unification_id[pmerge] = path
 
         merged_neighbors = []
-        for n, ((p, rid), (pm, rmid)) in enumerate(
-            zip(self.neighbors[path], self.neighbors[pmerge])
-        ):
+        for n, ((p, rid), (pm, rmid)) in enumerate(zip(self.neighbors[path], self.neighbors[pmerge])):
             if rid and rmid and rid != rmid:
-                raise ExploreError(
-                    f"neighbor {n} of '{path}'({rid}) and '{pmerge}'({rmid}) do not match"
-                )
+                raise ExploreError(f"neighbor {n} of '{path}'({rid}) and '{pmerge}'({rmid}) do not match")
             if rmid:
                 merged_neighbors.append((self._path(pm), rmid))
             else:
@@ -233,9 +225,7 @@ class Explore:
                 new.append((np_, rid))
                 if rid:
                     try:
-                        assert (
-                            np_ in self.rooms
-                        ), f"unify: path {np} {np_} of {(p, ns)} not in rooms"
+                        assert np_ in self.rooms, f"unify: path {np} {np_} of {(p, ns)} not in rooms"
                     except AssertionError as exc:
                         self.dump()
                         raise exc
@@ -261,11 +251,9 @@ class Explore:
                     yield d, path
 
     def is_explored(self):
-        return next(self.unexplored(), None) is None and all(
-            len(p) == 1 for p in self.room_ids.values()
-        )
+        return next(self.unexplored(), None) is None and all(len(p) == 1 for p in self.room_ids.values())
 
-    def guess(self, orig=None):
+    def guess(self, orig=None, start=Path()):
         aedi = graph.Aedificium(self.problem)
 
         ids = {}
@@ -280,22 +268,15 @@ class Explore:
             for src_door, (trg_path, _) in enumerate(ns):
                 src = (src_path, src_door)
                 trg_door = next(
-                    (
-                        j
-                        for j, (p, rid) in enumerate(self.neighbors[trg_path])
-                        if p == src_path
-                    ),
+                    (j for j, (p, rid) in enumerate(self.neighbors[trg_path]) if p == src_path),
                     None,
                 )
                 if trg_door is None:
-                    raise ExploreError(
-                        f"backlink not found: {(src, trg_path, self.neighbors[trg_path])}"
-                    )
+                    raise ExploreError(f"backlink not found: {(src, trg_path, self.neighbors[trg_path])}")
                 trg = (trg_path, trg_door)
 
                 if (src, trg) in connected or (trg, src) in connected:
                     continue
-                print(src, trg)
                 connected.add((src, trg))
                 connections.append(
                     {
@@ -314,7 +295,7 @@ class Explore:
 
         layout = {
             "rooms": [int(rooms[p]) for p in ids.keys()],
-            "startingRoom": ids[Path()],
+            "startingRoom": ids[start],
             "connections": connections,
         }
 
@@ -329,7 +310,7 @@ class Explore:
                 return ret
 
             for d, (q, _) in enumerate(self.neighbors[p]):
-                queue.append((q, Path([d])))
+                queue.append((q, ret + Path([d])))
 
         assert False, "return path not found"
 
@@ -367,75 +348,87 @@ def room_solve(problem, nrooms, plen):
     print("score", ex.score)
 
 
-def get_mark(rid):
-    return Path("[" + str(int(rid[0]) ^ 3) + "]")
+def get_mark(rid, mask):
+    return Path("[" + str(int(rid[0]) ^ mask) + "]")
 
 
-def mark_solve(problem, nrooms, plen):
-    ex0 = Explore(problem, [d + d + d + d + d + d for d in DOORS[:plen]])
-    api.select(ex0.problem)
-    res = ex0.explore(Path())
+def apply_mask(rid, mask):
+    return "".join(map(lambda d: str(int(d) & ~mask), rid))
 
-    ex0.update(Path(), res)
-    ex0.dump()
 
-    while True:
-        door, unexplored = next(ex0.unexplored(), (None, None))
-        if unexplored is None:
-            break
+def mark_solve(problem, nrooms):
+    probes = [d + d + d + d + d + d for d in DOORS[:2]]
+    api.select(problem)
 
-        print("explore", door, unexplored)
-        path = unexplored + Path([door])
-        res = ex0.explore(path)
-        ex0.update(path, res)
-        ex0.dump()
+    masks = [0, 1, 2]
+    exs = []
+    loop = Path()
+    mark_loop = Path()
 
-        ex0.unify_all()
-        ex0.dump()
+    for mask in masks:
+        print("exploration mask", mask)
+        if mask != 0:
+            for p, rid in exs[-1].rooms.items():
+                q = exs[-1].returnfrom(p)
+                loop = loop + p + q
+                mark_loop = mark_loop + p + get_mark(rid, mask) + q
 
-    print("found all rooms")
-    mark = Path()
-    for p, rid in ex0.rooms.items():
-        q = ex0.returnfrom(p)
-        mark = mark + p + get_mark(rid) + q
+            print("marked", mark_loop, loop)
+            assert exs[-1].walk(loop) == Path(), f"loop doesn't close {exs[-1].walk(loop)}"
 
-    print("marked", mark)
+        ex = Explore(problem, probes)
+        exs.append(ex)
 
-    ex1 = Explore(problem, [d + d + d + d + d + d for d in DOORS[:plen]])
-    res = ex1.explore(Path(), mark=mark)
-    ex1.update(Path(), res)
-    ex1.dump()
+        res = ex.explore(Path(), mark=mark_loop)
+        ex.update(Path(), res)
+        ex.dump()
 
-    while True:
-        door, unexplored = next(ex1.unexplored(), (None, None))
-        if unexplored is None:
+        while True:
+            door, unexplored = next(ex.unexplored(), (None, None))
+            if unexplored is None:
+                break
+
+            print("explore", door, unexplored)
+            path = unexplored + Path([door])
+            res = ex.explore(path, mark=mark_loop)
+            ex.update(path, res)
+            ex.unify_all()
+            ex.dump()
+
+        assert ex.is_explored(), "not fully explored"
+        if nrooms % len(ex.rooms) != 0:
+            raise ExploreError(f"not all rooms could be identifed {len(ex.rooms)}/{nrooms}")
+        if len(ex.rooms) == nrooms:
+            print("found all rooms")
             break
 
-        print("explore", door, unexplored)
-        path = unexplored + Path([door])
-        res = ex1.explore(path, mark=mark)
-        ex1.update(path, res)
-        ex1.dump()
-
-        ex1.unify_all()
-        ex1.dump()
-
-    print("explored", ex1.is_explored())
-    if ex1.is_explored():
-        # get old markings
-        orig = {}
-        for path in ex1.rooms.keys():
-            p = ex0.walk(path)
-            rid = ex0.rooms[p]
-            orig[path] = rid[0]
-            print(path, p, rid)
-
-        ex0.dump()
-        ex1.dump()
-        print(orig)
-        print("guess", ex1.guess(orig=orig))
-    print("score", ex0.score + ex1.score)
-    assert False
+    if len(ex.rooms) != nrooms:
+        raise ExploreError(f"not all rooms could be identifed {len(ex.rooms)}/{nrooms}")
+    for e in exs:
+        e.dump()
+
+    # get old markings
+    orig = {}
+    for path in ex.rooms.keys():
+        p = exs[0].walk(path)
+        rid = exs[0].rooms[p]
+        orig[path] = rid[0]
+        print(path, p, rid)
+    print(orig)
+    # try to identify original start
+    start = apply_mask(exs[0].rooms[Path()], mask)
+    starts = []
+    all_masked = []
+    for p, rid in ex.rooms.items():
+        mrid = apply_mask(rid, mask)
+        all_masked.append(mrid)
+        if mrid == start:
+            starts.append(p)
+    print("start", start, starts, all_masked)
+    assert len(starts) > 0
+
+    print("guess", ex.guess(orig=orig, start=starts[0]))
+    print("score", sum(e.score for e in exs))
 
 
 def path_solve(problem, nrooms, plen):
@@ -498,23 +491,17 @@ if __name__ == "__main__":
     with open(os.path.join("..", "problems.json")) as h:
         problems = json.loads(h.read())
 
-        problems = {
-            p["problem"]: {"size": p["size"], "idx": i} for i, p in enumerate(problems)
-        }
+        problems = {p["problem"]: {"size": p["size"], "idx": i} for i, p in enumerate(problems)}
 
     if problem not in problems:
         raise ExploreError(f"unknown problem {problem}")
 
     try:
-        if problems[problem]["idx"] < 6:
-            room_solve(problem, problems[problem]["size"], int(sys.argv[2]))
-        else:
-            mark_solve(problem, problems[problem]["size"], int(sys.argv[2]))
-
+        mark_solve(problem, problems[problem]["size"])
         api.clean_explore_cache()
-        # except ExploreError as exc:
-        #     api.clean_explore_cache()
-        #     raise exc
+    except ExploreError as exc:
+        api.clean_explore_cache()
+        raise exc
     except Exception as exc:
         api.write_explore_cache()
         raise exc