import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int t = sc.nextInt();
    for(int i = 0; i < t; i++) {
      String s = sc.next();
      int len = s.length();
      int[] w = new int[len];
      int[] g = new int[len];
      int[] r = new int[len];
      int w1 = 0;
      int g1 = 0;
      int p = 0;
      for(int j = 0; j < len; j++) {
        if(s.charAt(j) == 'W') {
          if(j == 0) w[j]++;
          if(j > 0) w[j] = w[j - 1] + 1;
          w1 = j;
        } else if(s.charAt(j) == 'G') {
          if(j == 0) g[j]++;
          if(j > 0) g[j] = g[j - 1] + 1;
          g1 = j;
        } else {
          if(j == 0) r[j]++;
          if(j > 0) r[j] = r[j - 1] + 1;
        }
        if((w[j] < g[j]) || (g[j] < r[j])) p++;
      }
      String ans = "impossible";
      if((p == 0) && (g[len - 1] == r[len - 1]) && (w1 < g1)) ans = "possible";
      System.out.println(ans);
    }
  }
}