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