#include <bits/stdc++.h>

int main() {
    int t;
    std::cin >> t;
    while (t--) {
        std::string s;
        std::cin >> s;
        if (s[s.size() - 1] != 'R' || s[s.size() - 2] != 'G') {
            std::cout << "impossible" << std::endl;
            continue;
        }
        bool flg = true;
        int a = 0, w = 0;
        std::deque<int> q;
        for (auto c : s) {
            switch (c) {
                case 'W':
                w++;
                break;
                case 'G':
                q.push_back(1);
                a = std::max(a, (int)q.size());
                break;
                case 'R':
                if (q.size() == 0) {
                    goto g;
                } else {
                    q.pop_back();
                }
            }
        }
        std::cout << (q.size() == 0 && w >= a ? "possible" : "impossible") << std::endl;
        continue;
g:
        std::cout << "impossible" << std::endl;
    }
    return 0;
}