#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

void solve() {
	string S;
	cin >> S;
	int a = 0, b = 0;
	bool w = false;
	bool res = true;
	REP(i, S.length()) {
		if (S[i] == 'W') {
			++a;
			w = true;
		}
		else if (S[i] == 'G') {
			--a;
			w = false;
			if (a < 0) res = false;
			++b;
		}
		else {
			--b;
			if (b < 0) res = false;
		}
	}
	if (b != 0) res = false;
	if (w) res = false;
	cout << (res ? "possible" : "impossible") << endl;
}

int main(int argc, char **argv) {
	int T;
	cin >> T;
	REP(i, T) solve();
	return 0;
}