T = int(input())

for i in range(T):
    s = input()    
    L = len(s)
    wg = 0
    gr = 0
    f = True
    for i in range(L):
        if s[i] == 'W' :
            wg += 1
        elif s[i] == 'G':
            wg -= 1
            gr += 1
        elif s[i] == 'R':
            gr -= 1
        if  not(0 <= gr and 0 <= wg):
            print('impossible')      
            break
        
        if s[L-i-1] == 'G':
            f = False
        if f and s[L-i-1] == 'W':
            print('impossible')      
            break
    else:
        if gr == 0:
            print('possible')
        else:
            print('impossible')