#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <string.h>
#include <vector>
using namespace std;

#define ll long long
#define INF (1 << 30)
#define INFLL (1LL << 60)

#define FOR(i,a,b) for(ll i = (a);i<(b);i++)
#define REP(i,a) FOR(i,0,(a))
#define MP make_pair

bool check(string str){
	int w = 0, g = 0, r = 0;
	bool flag = false;
	int flag2 = 0;

	for(int i = 0;i < str.size();i++){
		if(str[i] == 'W'){
			flag = true;
			w++;
			flag2 = 0;
		}else if(str[i] == 'G'){
			flag = true;
			if(w < g + 1) return false;
			g++;
			if(flag2 == 0) flag2 = 1;
		}else{
			flag = false;
			if(w < r + 1 || g < r + 1) return false;
			r++;
			if(flag2 == 1) flag2 = 2;
		}
	}

	if(flag || flag2 != 2) return false;
	if(g != r) return false;

	return true;
}

int main() {
	int n;
	string str;

	cin >> n;
	for(int i = 0;i < n;i++){
		cin >> str;
		bool ans = check(str);
		if(ans) cout << "possible" << endl;
		else cout << "impossible" << endl;
	}
	return 0;
}