pt path h (Parent _ l r) =
   if h < leastHash l then noAns
   else if h < leastHash r then pt (path ++ [Left $ branch l]) h (branch l)
   else pt (path ++ [Right $ branch r]) h (branch r)
pt path h (Parent _ l r) =
   if h < leastHash l then noAns
   else if h < leastHash r then pt (path ++ [Left $ branch l]) h (branch l)
   else pt (path ++ [Right $ branch r]) h (branch r)
pt path h (Parent _ l r) =
   if h < leastHash l then noAns
   else if h < leastHash r then pt (path ++ [Left $ branch l]) h (branch l)
   else pt (path ++ [Right $ branch r]) h (branch r)