#include <string>
#include <iostream>
#include <algorithm>
bool check(const std::string& l)
{
	using std::size_t;
	if (l.size() < 3 || 'R' != l.back()) return false;
	size_t r = l.size() - 1;
	size_t g = l.find_last_of('G', l.size() - 2);
	size_t w = l.find_last_of('W', g);
	while (
		std::string::npos != r && 0 != r
		&& std::string::npos != g && 0 != g//Rより前にGがあるか
		&& std::string::npos != w && 0 != w//Gより前にWがあるか
	) {
		r = l.find_last_of('R', r - 1);
		g = l.find_last_of('G', std::min(g - 1, r));
		w = l.find_last_of('W', std::min(w - 1, g));
	}
	return (0 == w || (std::string::npos == r && std::string::npos == l.find_last_of('G', w - 1)));
}
int main()
{
	const auto n = []() { std::string buf; std::getline(std::cin, buf); return static_cast<std::size_t>(std::stoul(buf)); }();
	std::string buf;
	const char* re[] = { "impossible", "possible" };
	for (std::size_t i = 0; i < n && std::getline(std::cin, buf); ++i) {
		const auto r = check(buf.substr(0, buf.find_last_not_of('\n') + 1));
		std::cout << re[r] << std::endl;
	}
}