#include <bits/stdc++.h>

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long ll;

const double EPS = 1e-8;
const int INF = 1e9;
const int MOD = 1e9+7;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

bool ok(string s){
	int w,g;
	w = g = 0;
	int last = -1;
	for(int i=s.size()-1;i>=0;i--)if(s[i] == 'G'){last = i;break;}
	if(s.size() < 3)return false;

	for(int i=0;i<s.size();i++){
		if(s[i] == 'W')w++;
		else if(s[i] == 'G'){
			w--;
			g++;
		}else{
			g--;
		}
		if(w < 0 || g < 0)return false;
		if(last < i && s[i] == 'W')return false;
	}
	if(g != 0)return false;

	return true;
}

int main(void) {
	int n;
	cin >> n;
	for(int i=0;i<n;i++){
		string s;
		cin >> s;
		if(ok(s))cout << "possible" << endl;
		else cout << "impossible" << endl;
	}


	return 0;
}