#include <bits/stdc++.h>
using namespace std;
#define FOR(i, n) for(int i = 0; i < (n); i++)
#define FORR(x, arr) for(auto& x:arr)
#define ITR(x, c) for(__typeof(c.begin()) x=c.begin();x!=c.end();x++)
#define MEM(a, x) memset(a, x, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define UNIQUE(a) a.erase(unique(ALL(a)), a.end())
typedef long long ll;
typedef pair<int, int> P;

int n;

int main(int argc, char const *argv[]) {
	ios_base::sync_with_stdio(false);
	cin >> n;
	vector<string> v(n);
	FOR(i, n) {
		string s;
		cin >> s;
		int g = 0, r = 0, w = 0, p = 1<<30, q = 0, G = 0, y = 0;
		bool ok = true;
		FOR(i, s.size()) {
			if (s[i]=='W') w++;
			else if (s[i]=='G') {
				g++;
				G++;
				y = max(y, i);
			}
			else {
				r++;
				G--;
				if (G < 0) ok = false;
				p = min(p, i);
				q = max(q, i);
			}
		}
		for (int i = y; i <= q; i++) {
			if (s[i]=='W') ok = false;
		}
		if (g != r || w < g || p<=0 || s[p-1]!='G' || q!=s.size()-1) ok = false;
		v[i] = (ok ? "possible" : "impossible");
	}
	FOR(i, n) cout << v[i] << endl;
	return 0;
}