t = int(raw_input())
for _ in range(t):
    s = raw_input()
    ans = True
    cnt = 0
    for c in s:
        if c == 'G':
            cnt += 1
        elif c == 'R':
            cnt -= 1
            if cnt < 0:
                ans = False
                break
    if cnt != 0 or s[len(s)-2:] != 'GR':
        ans = False
    if ans:
        print 'possible'
    else:
        print 'impossible'