diff --git a/amrun.cabal b/amrun.cabal
--- a/amrun.cabal
+++ b/amrun.cabal
@@ -1,5 +1,5 @@
 Name:                amrun
-Version:             0.0
+Version:             0.0.0.1
 Synopsis:            Interpreter for AM
 Description:         The package contains an interpreter for the AM-Language that is introduced in the basic programming course \"Algorithmisches Denken und imperative Programmierung\" (WS 2011/12 and later) at the University of Bonn.
 License:             GPL
diff --git a/src/amrun.hs b/src/amrun.hs
--- a/src/amrun.hs
+++ b/src/amrun.hs
@@ -147,10 +147,14 @@
    Just c -> return c
    Nothing -> 
      case oneArgCmd of
-       Just c -> do{arg <- (pcParser <?> "command argument"); return (c arg);}
+       Just c -> do
+                   sign <- if cmd == "LIT" then neg else return 1
+                   arg <- (pcParser <?> "command argument")
+                   return (c (sign*arg))
        Nothing -> unexpected (cmd ++ " is not a command.")
                    }
   where
+    neg = spaces >> (try (char '-' >> ((many1 space >> fail "spaces after '-', expected digit") <|> return (-1))) <|> return 1)
     readCmd cmd = case cmd of
                    "ADD" -> Just ADD
                    "MUL" -> Just MUL