for _ in range(int(input())):
    s=list(input())
    s.reverse()
    a,b,c=0,0,0;d=1;t=0
    for i in s:
        if i=="R":
            a+=1
        elif i=="G":
            b+=1;t+=1
            if a<b:
                d=0;break
        else:
            if not a or not b:
                d=0;break
            if t:
            	t-=1
            c+=1
    if a!=b or c<a or t:
        d=0
    print("possible" if d else "impossible")