T = int(input())
for _ in range(T):
    S = input().strip()
    count_G = S.count('G')
    count_R = S.count('R')
    count_W = S.count('W')
    
    if count_G != count_R:
        print("impossible")
        continue
    if count_W < count_G:
        print("impossible")
        continue
    
    available_W = 0
    available_G = 0
    possible = True
    
    for c in S:
        if c == 'W':
            available_W += 1
        elif c == 'G':
            if available_W < 1:
                possible = False
                break
            available_W -= 1
            available_G += 1
        elif c == 'R':
            if available_G < 1:
                possible = False
                break
            available_G -= 1
    
    if possible and available_G == 0:
        print("possible")
    else:
        print("impossible")