#include <stdio.h>
#include <string.h>

int main(void)
{
	char S[1001];
	int T, length, tmp1, tmp2, tmp3, i, j;
	scanf("%d", &T);
	for (i = 0; i < T; ++i) {
		scanf("%s", S);
		length = strlen(S);
		tmp1 = 0;
		tmp2 = 0;
		tmp3 = 0;
		for (j = 0; j < length; ++j) {
			if (S[j] == 'W') {
				++tmp1;
				tmp2 = 1;
			}
			else if (S[j] == 'G') {
				if (tmp1 == 0) break;
				--tmp1;
				tmp2 = 0;
				++tmp3;
			}	
			else {
				if (tmp3 == 0) break;
				--tmp3;
			}
		}
		if (j != length || tmp2 || tmp3) puts("impossible");
		else puts("possible");
	}
	return 0;
}