Hopscotch
Output: Standard Output (stdout)
Memory limit: 32 megabytes
Time limit: 5.0 seconds
While it commonly refers to the popular children's jumping game, Hopscotch is also the name of the most adorable rabbit (in the world). Hopscotch is a simple creature, and spends his entire existence in one of three states: sleeping, exploring, and nibbling.
 When Hopscotch is sleeping, he can either keep sleeping or wake up and begin exploring.
 When Hopscotch is exploring, he will inevitably find something he considers to be edible, and begin nibbling.
 When Hopscotch is nibbling, he will either return to exploring or spontaneously begin sleeping.
We have been trying to document Hopscotch's day. We've recorded a log of N states that we've observed Hopscotch in. Unfortunately, Hopscotch is very fast and we're worried that we might have missed recording a state. Given our log of the N recorded states, please tell us whether they describe a plausible sequence (the state transitions follow the rules described above) or whether the sequence described is impossible. The sequence may begin in any state.
Input
The first line will contain a single nonnegative integer N, describing the number of states that have been recorded in the log.
The following N lines each contain a single character representing the recorded state. 'S' represents sleeping, 'E' represents exploring, and 'N' represents nibbling.
Output
If the sequence described is plausible, output a single line containing the text plausible
(without quotes).
If the sequence described is impossible, output a single line containing the text impossible
(without quotes).
Subtasks
 Subtask 1 (20%): N \leq 1,000, the sequence only contains entries of sleeping.
 Subtask 2 (30%): N \leq 1,000, the sequence contains no entries of sleeping.
 Subtask 3 (50%): N \leq 1,000,000, no further restrictions apply.

Sample Input 1
10 S S S E N S S S E N
Sample Output 1
plausible

Sample Input 2
10 E N N E E N S S E N
Sample Output 2
impossible