A long time ago one man said that he had explored the corridors of one

A long time ago one man said that he had explored the corridors of one cave. This means that he was in all corridors of the cave. Corridors are really horizontal or vertical segments. A corridor is treated as visited if he was in at least one point of the corridor.
Now you want to know if this is true. You have a map of the cave, and you know that the explorer used the following algorithm: he turns left if he can, if he can't he goes straight, if he can't he turns right, if he can't he turns back. Exploration ends when the man reaches the entry point for the second time. Your task to count how many corridors weren't visited by explorer.
Input
In the first line there is an integer T (T