#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("possible");}else{puts("impossible");}
#define MAX_N 200005

int main() {
    int T;
    cin >> T;
    rep(_,T){
        string s;
        cin >> s;
        int n = s.size();
        int r = 0, g = 0, w = 0;
        int ng = 0;
        drep(i,n){
            if(s[i] == 'R') r++;
            else if(s[i] == 'G') g++;
            else w++;
            if(r < g || (g == 0 && w > 0)){
                ng = 1;
                break;
            }
        }
        if(ng == 1 || r == 0 || r != g || s[n-1] != 'R' || w < r) {
            cout << "impossible" << endl;
            continue;
        }
        r = 0;
        g = 0;
        w = 0;
        drep(i,n){
            if(s[i] == 'R'){
                r++;
            }else if(s[i] == 'G'){
                g = min(g+1,r);
            }else{
                w = min(w+1,g);
            }
        }
        if(w != r) ng = 1;
        if(ng == 0)yn;
    }
    return 0;
}