t = int(input())
ans = []
for i in range(t):
    s = list(input())
    count = 0
    f = 0
    if len(s) < 3:
        ans.append('impossible')
        continue
    while(len(s)):
        wgr = s.pop(0)
        if wgr == 'W':
            continue
        elif wgr == 'G':
            count += 1
        elif wgr == 'R':
            count -= 1
        if count < 0:
            f = 1
    if f == 0 and count == 0:
        ans.append('possible')
    else:
        ans.append('impossible')
for j in ans:
    print(j)