#include <iostream>
using namespace std;

int main(){
    int t;
    cin >> t;
    while(t--){
        string s;
        cin >> s;
        int w = 0,g = 0,wcount =0;
        bool f = true;
        for(int i =0;i < s.size();i++){
            if(s[i] == 'W') w++;
            if(s[i] == 'G'){
                wcount += --w;
                w = 0;
                g++;
                if(wcount < 0){
                    cout << "impossible" << endl;
                    f = false;
                    break;
                }
            }
            if(s[i] == 'R' && --g < 0){
                cout << "impossible" << endl;
                f = false;
                break;
            }
        }
        if(f) cout << (w == 0 && g == 0 ? "possible" : "impossible") << endl;
    }
}