N=int(input())

for i in range(N):
    S=input()
    ans=0
    cnt=0
    R=0
    G=0
    for j in range(len(S)):
        if S[j]=="G":
            ans+=1
            G+=1
        elif S[j]=="R":
            ans-=1
            R+=1
            if ans<0:
                print("impossible")
                R=0
                j=len(S)
        else:
            cnt+=1
        if len(S)==cnt+R+G:
            if ans==0:
                print("possible")
            else:
                print("impossible")