import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import itertools

T = int(readline())
words = read().decode().split()

def solve(word):
    n = word.rfind('R')
    if n != len(word) - 1:
        return False
    word = word.replace('W','')
    A = tuple(itertools.accumulate(1 if x == 'G' else -1 for x in word))
    return all(x >= 0 for x in A) and (A[-1] == 0)

answers = ('possible' if solve(w) else 'impossible' for w in words)
print('\n'.join(answers))