#include<bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int> > vii;
#define rrep(i, m, n) for(int (i)=(m); (i)<(n);  (i)++)
#define erep(i, m, n) for(int (i)=(m); (i)<=(n); (i)++)
#define  rep(i, n)    for(int (i)=0; (i)<(n);  (i)++)
#define rrev(i, m, n) for(int (i)=(n)-1; (i)>=(m); (i)--)
#define erev(i, m, n) for(int (i)=(n); (i)>=(m); (i)--)
#define  rev(i, n)    for(int (i)=(n)-1; (i)>=0; (i)--)
#define vrep(i, c)    for(__typeof((c).begin())i=(c).begin(); i!=(c).end(); i++)
#define  ALL(v)       (v).begin(), (v).end()
#define mp            make_pair
#define pb            push_back
template<class T, class S> inline bool minup(T& m, S x){ return m>(T)x ? (m=(T)x, true) : false; }
template<class T, class S> inline bool maxup(T& m, S x){ return m<(T)x ? (m=(T)x, true) : false; }

const int    INF = 1000000000;
const ll     MOD = 1000000007LL;
const double EPS = 1E-12;

int T;
string s;

int main()
{
  cin >> T;

  while(T--){
    int G = 0;
    int R = 0;
    int GR = 0;
    int W = 0;
    bool ok = false;
    cin >> s;
    if(s.size() < 3){
      puts("impossible");
      continue;
    }
    rep(i, s.size()){
      if(s[i] == 'G'){
        if(W > 0){
          ok = false;
          W -= 1;
        }
        GR += 1;
        G += 1;
      }
      if(s[i] == 'R'){
        //if(W > 0) W -= 1;
        GR -= 1;
        R += 1;
      }
      if(s[i] == 'W') if(G > 0 && !ok){
          ok = true;
          //      if(s[i-1] != 'G') continue;
          while(s[i+1] == 'W') i++;
          W += 1;
        }
      if(GR < 0) break;
    }
    if(G < 1 || R < 1 || G != R) GR = -1;
    if(W > 0) GR = -1;
    puts(GR ? "impossible" : "possible");


    //    cerr << W << " " << G << " " << R << endl;
  }

  return 0;
}