import java.util.*;
import java.io.*;

public class Main {
	public static void main (String[] args) throws Exception {
	    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	    int n = Integer.parseInt(br.readLine());
	    StringBuilder sb = new StringBuilder();
	    for (int i = 0; i < n; i++) {
	        char[] arr = br.readLine().toCharArray();
	        int r = 0;
	        int g = 0;
	        int w = 0;
	        boolean type = true;
	        for (int j = arr.length - 1; j >= 0; j--) {
	            if (arr[j] == 'W') {
	                if (g > 0) {
	                    g--;
	                    w++;
	                } else if (g == 0 && w == 0) {
	                    type = false;
	                    break;
	                }
	            } else if (arr[j] == 'G') {
	                if (r == 0) {
	                    type = false;
	                    break;
	                }
	                r--;
	                g++;
	            } else {
	                r++;
	            }
	        }
	        if (r > 0 || g > 0) {
	            type = false;
	        }
	        if (type) {
	            sb.append("possible");
	        } else {
	            sb.append("impossible");
	        }
	        sb.append("\n");
	    }
		System.out.print(sb);
    }
}