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
    
    current_g = 0
    current_r = 0
    w_so_far = 0
    possible = True
    
    for c in S:
        if c == 'W':
            w_so_far += 1
        elif c == 'G':
            current_g += 1
            if w_so_far < current_g:
                possible = False
                break
        elif c == 'R':
            current_r += 1
            if current_r > current_g:
                possible = False
                break
    
    print("possible" if possible else "impossible")