count = int(input())
result_list = []

for i in range(count):
    memo = input()
    result = "possible"
    green_flg = 0
    judge = 0
    for char in reversed(memo):
        if char == 'R':
            judge += 1
        elif char == 'G':
            green_flg = 1
            judge -= 1
            if judge < 0:
                result = "impossible"
                break
        else:
            if green_flg == 0:
                result = "impossible"
                break
    
    result_list.append(result)
    
for r in result_list:
    print(r)