for _ in range(int(input())):
    s = input()
    n = len(s)
    r = 0
    GR = False
    for i in range(n - 1, -1, -1):
        if s[i] == 'R':
            r += 1
        elif s[i] == 'G':
            r -= 1
            if r == -1:
                break
            GR = True
        else:
            if not GR:
                break
    if r != 0 or not GR:
        print("impossible")
    else:
        print("possible")