#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;

bool solve(string s) {
  const int n = s.size();
  int W = 0;
  int WW = 0;
  int G = 0;

  for (int i = 0; i < n; i++) {
    if (s[i] == 'W') {
      W++;
      WW++;
    } else if (s[i] == 'G') {
      WW = 0;
      W--;
      G++;
    } else {
      G--;
    }
    if (W < 0 || G < 0) return false;
  }

  return G == 0 && WW == 0;
}

int main() {
  int T;
  cin >> T;
  while (T--) {
    string s;
    cin >> s;

    cout << (solve(s) ? "possible" : "impossible") << endl;
  }
}