T = int(input())
tt=[]
for _ in range(T):
    tt.append(input())
for t in tt:
    t = list(t)
    if len(t)<3:
        print("impossible")
        continue
    countW=0
    countG=0
    countR=0
    Flag=True
    FlagW=False
    for i in t:
        if i=="G":
            countG+=1
        elif i=="R":
            countR+=1
            FlagW=True
        else:
            countW+=1
            FlagW=False

        if countG-countR<0:
            Flag=False
            continue
    countG2=0
    countW2=0
    countR2=0
    if not t[:-2]=="G" and t[:-1]=="R":
        Flag=False

    if countG!=countR or not Flag or not FlagW:
        print("impossible")
    else:
        print("possible")