T = int(input())
for _ in range(T):
    s = input().strip()
    if not s:
        print("impossible")
        continue
    # Check if the last character is R
    if s[-1] != 'R':
        print("impossible")
        continue
    # Check if the counts of G and R are equal
    count_g = s.count('G')
    count_r = s.count('R')
    if count_g != count_r:
        print("impossible")
        continue
    # Check that R counts never exceed G counts at any position
    current_g = 0
    current_r = 0
    possible = True
    for c in s:
        if c == 'G':
            current_g += 1
        elif c == 'R':
            current_r += 1
        if current_r > current_g:
            possible = False
            break
    if not possible:
        print("impossible")
        continue
    # Check that each G has at least one W before it
    g_positions = [i for i, char in enumerate(s) if char == 'G']
    for pos in g_positions:
        if 'W' not in s[:pos]:
            possible = False
            break
    print("possible" if possible else "impossible")