def solve(S):
    d = {'W': 0, 'G': 0, 'R': 0}
    for s in reversed(S):
        if s == 'G' and d['R'] == 0:
            return False
        elif s == 'W' and d['G'] == 0:
            return False
        d[s] += 1
        if d['G'] > d['R']:
            return False
    return True if d['W'] >= d['G'] == d['R'] and 0 not in d.values() else False


N = int(input())

for _ in range(N):
    print('possible' if solve(input()) else 'impossible')