import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 7)


def main():
    S = input().rstrip()
    W = 0
    G = 0
    for s in S:
        if s == "W":
            W += 1
        elif s == "G":
            if not W:
                return False
            W -= 1
            G += 1
        else:
            if not G:
                return False
            G -= 1
    return G == 0


T = int(input())
for _ in range(T):
    if main():
        print("possible")
    else:
        print("impossible")