TT = int(input())

for loop in range(TT):

    S = input()

    ans = "possible"

    a = [0,0,0]
    for v in reversed(S):
        if v == "R":
            a[0] += 1
        if v == "G":
            if a[0] == 0:
                ans = "impossible"
                break
            else:
                a[0] -= 1
                a[1] += 1
        if v == "W":
            if a[1] + a[2] == 0:
                ans = "impossible"
                break
            elif a[1] > 0:
                a[1] -= 1
                a[2] += 1

    if a[0] + a[1] != 0:
        ans = "impossible"

    print (ans)