diff --git a/harald/explore.py b/harald/explore.py
old mode 100644
new mode 100755
index 7b7bb3a..3d9e112
--- a/harald/explore.py
+++ b/harald/explore.py
@@ -1,5 +1,10 @@
+#!/usr/bin/env python3
+
 import api
 import functools
+import json
+import os.path
+import sys
 from collections import defaultdict
 
 
@@ -13,7 +18,7 @@ class Path:
         self.path = path
 
     def __repr__(self):
-        return "." +self.path if self.path else "."
+        return "." + self.path if self.path else "."
 
     def __bool__(self):
         return bool(self.path)
@@ -38,10 +43,11 @@ class Path:
 
     def shorten(self, path, pmerge):
         if self.path.startswith(pmerge.path):
-            return Path(path.path + self.path[len(pmerge.path):])
+            return Path(path.path + self.path[len(pmerge.path) :])
         else:
             return self
 
+
 class Explore:
     def __init__(self, problem):
         self.problem = problem
@@ -131,78 +137,53 @@ class Explore:
             raise ExploreError(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)
         room_id = self.rooms[path]
 
-        rooms = self.rooms.copy()
-        room_ids = self.room_ids.copy()
-        neighbors = self.neighbors.copy()
-        unifications = self.unifications.copy()
-        unification_id = self.unification_id.copy()
-
         merged_neighbors = []
-        for n, ((p, rid), (pm, rmid)) in enumerate(
-            zip(neighbors[path], 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")
             merged_neighbors.append((p.shorten(path, pmerge), rid or rmid))
 
         # unify paths
-        unification_id[pmerge] = path
-        for p in unifications[pmerge]:
-            unification_id[p] = path
+        self.unification_id[pmerge] = path
+        for p in self.unifications[pmerge]:
+            self.unification_id[p] = path
 
-        unifications[path] = unifications[path1] | unifications[path2] | {pmerge}
-        if pmerge in unifications:
-            del unifications[pmerge]
+        self.unifications[path] = self.unifications[path1] | self.unifications[path2] | {pmerge}
+        if pmerge in self.unifications:
+            del self.unifications[pmerge]
 
         # fix rooms
-        del rooms[pmerge]
+        del self.rooms[pmerge]
 
-        room_ids[room_id] = {p for p in room_ids[room_id] if p != pmerge}
+        self.room_ids[room_id] = {p for p in self.room_ids[room_id] if p != pmerge}
 
-        neighbors[path] = merged_neighbors
-        del neighbors[pmerge]
-        for p, ns in neighbors.items():
+        self.neighbors[path] = merged_neighbors
+        del self.neighbors[pmerge]
+        for p, ns in self.neighbors.items():
             new = []
             for np, rid in ns:
                 np = np.shorten(path, pmerge)
                 new.append((np, rid))
                 if rid:
-                    assert np in rooms, f"path {np} of {(p,ns)} not in rooms"
-            neighbors[p] = new
-
-        unified = self.__class__(self.problem)
-        unified.rooms = rooms
-        unified.room_ids = room_ids
-        unified.neighbors = neighbors
-        unified.unifications = unifications
-        unified.unification_id = unification_id
-
-        return unified
+                    assert np in self.rooms, f"path {np} of {(p, ns)} not in rooms"
+            self.neighbors[p] = new
 
     def unify_all(self):
-        unified = self
-
         while True:
-            for rid, paths in unified.room_ids.items():
+            for rid, paths in self.room_ids.items():
                 if len(paths) > 1:
                     paths = list(paths)
                     print("unify", paths[0], paths[1])
-                    unified = unified.unify(paths[0], paths[1])
+                    self.unify(paths[0], paths[1])
                     break
             break
 
-        return unified
-
     def unexplored(self):
         for path, ns in self.neighbors.items():
             for p, rid in ns:
@@ -210,9 +191,7 @@ class Explore:
                     yield p
 
     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):
         ids = {}
@@ -225,11 +204,7 @@ class Explore:
             src_id = self.rooms[path]
             for src_door, (trg_path, trg_id) in enumerate(ns):
                 src = (src_id, src_door)
-                trg_door = next(
-                    j
-                    for j, (p, rid) in enumerate(self.neighbors[trg_path])
-                    if rid == src_id
-                )
+                trg_door = next(j for j, (p, rid) in enumerate(self.neighbors[trg_path]) if rid == src_id)
                 trg = (trg_id, trg_door)
 
                 if (src, trg) in connected or (trg, src) in connected:
@@ -268,7 +243,7 @@ def solve(problem):
         ex.dump()
 
         print("unify")
-        ex = ex.unify_all()
+        ex.unify_all()
         ex.dump()
 
     print("explored", ex.is_explored())
@@ -279,5 +254,14 @@ def solve(problem):
 if __name__ == "__main__":
     # with open("test.rooms") as h:
     #    obj = ast.literal_eval(h.read())
+    problem = sys.argv[1]
+
+    with open(os.path.join("..", "problems.json")) as h:
+        problems = json.loads(h.read())
+
+        problems = {p["problem"]: {"size": p["size"]} for p in problems}
+
+    if problem not in problems:
+        raise ExploreError(f"unknown problem {problem}")
 
-    solve("primus")
+    solve(problem)
diff --git a/Prob.json b/problems.json
similarity index 100%
rename from Prob.json
rename to problems.json