t = int(input())
ans = []
for i in range(t):
    s = list(input())
    ss = list(s)
    f = 0
    flag = 1
    count = 0
    count_w = 0
    count_g = 0
    count_r = 0
    while(s):
        wgr = s.pop(0)
        if wgr == 'W':
            flag = 1
            count_w += 1
            continue
        elif wgr == 'G':
            count += 1
            count_g += 1
            flag = 0
        elif wgr == 'R':
            count -= 1
            count_r += 1
        if count < 0:
            f = 1
    if f == 0 and count == 0 and flag == 0:
        ans.append('possible')
    else:
        ans.append('impossible')
for j in ans:
    print(j)