#include<iostream>
#include<string>

using namespace std;

int main(){
    int n;
    cin >> n;
    for(int i = 0; i < n; i++){
        string s;
        cin >> s;
        int c = 0, wc = 0;
        bool f = false;
        for(int j = 0; j < s.size(); j++){
            if(s[j] == 'W'){
                f = false;
                wc++;
            }else if(s[j] == 'G'){
                f = true;
                c++;
                wc--;
            }else{
                c--;
            }
            if(c < 0 || wc < 0){
                f = false;
                break;
            }
        }
        cout << ((f && c == 0)? "possible":"impossible") << endl;
    }
    return 0;
}