for _ in range(int(input())):
    S = input()
    a = 0
    f = True
    for s in S:
        if s == "G":
            a += 1
        if s == "R":
            a -= 1
        if a < 0:
            f = False
    if not f or a != 0:
        print("impossible")
    else:
        print("possible")