for _ in range(int(input())):
    g = 0
    for c in input():
        if c == 'G':
            g += 1
        if c == 'R':
            if g > 0:
                g -= 1
            else:
                print('impossible')
                break
    else:
        if g == 0:
            print('possible')
        else:
            print('impossible')