#include <cstdio>
#include <iostream>
#include <cmath>
#include <string>
#define rep(n) for(int i = 0; i < n; ++i)
using namespace std;
int main(void) {
	int t;
	cin >> t;
	rep(t) {
		int c = 0, log = 0, count = 0;
		bool flag = true;
		string str;
		cin >> str;
		if (str.size() == 'W') { 
			cout << "impossible" << endl;
			break;
		}
		if(str.size())
		rep(str.size()) {
			if (str[i] == 'G') {
				++c, ++count;
				if (!log && i != str.size() - 1) {
					if (str[i + 1] == 'W') {
						log = 1;
					}
					else {
						log = 2;
					}
				}
			}
			else if (str[i] == 'R') {
				--c;
			}
			if (c < 0) {
				flag = false;
				break;
			}
		}
		if (count == 1 && log == 1) {
			flag = false;
		}
		if (flag) {
			if (c == 0) {
				cout << "possible" << endl;
			}
			else {
				cout << "impossible" << endl;
			}
		}
		else {
			cout << "impossible" << endl;
		}
	}
}