def solve(s):
    numG, numR = s.count('G'), s.count('R')
    if numG != numR or numG == 0:
        return False
    stacks = []
    for light in s:
        if light == 'R':
            stacks.append(1)
        elif light == 'G':
            for i in xrange(len(stacks)):
                if stacks[i] == 1:
                    stacks[i] += 1
                    break
            else:
                return False
        else:
            if len(stacks) == 0 or max(stacks) == 1:
                return False
            for i in xrange(len(stacks)):
                if stacks[i] == 2:
                    stacks[i] += 1
                    if len(stacks) == numG and min(stacks) == 3:
                        return True
                    break
    return True

for t in xrange(input()):
    print 'possible' if solve(raw_input()[::-1]) else 'impossible'