T=int(input())
for tests in range(T):
    S=input()

    W=0
    G=0
    R=0
    flag=1

    lastw=-1
    lastg=-1
    lastr=-1

    for ind in range(len(S)):
        s=S[ind]
        if s=="G":
            G+=1
            lastg=ind
        elif s=="R":
            R+=1
            lastr=ind
        else:
            W+=1
            lastw=ind
        if G<R:
            flag=0
        if W<G or W<R:
            flag=0

    if G==R and flag==1 and lastw<lastr and lastw<lastg and lastg<lastr:
        print("possible")
    else:
        print("impossible")