NIT director is very frustrated of zeheris and he decided to call police to catch the all of them. Director consulted a psychologist to know the psychology of zeheris in order to make it easy for the police to catch them.They took help of a psychologist who can predict where the zeheri will move if he is in a particular section of NIT. for example if NIT is divided in a 2 X 2 Grid. Psychologist matrix might be

S S
N N

So, here if a person is at 1,1 he can only move to south. S represents that he will move to south N represents that he will move to north W represents that he will move to west E represents that he will move to east.

What is the minimum number of police jeeps required to catch all the zeheris. No of jeeps required here are two only.

PS: You may assume that no zeheri tend to move outside NIT.

Constriants : N<500 and t<50