/*  This Code is Submitted by wywcgs for Problem 1022 on 2005-12-13 at 16:23:16 */ 
#include <cstdio>

const int MAX = 128;

class Unit {
public:
	int id;
	int check[2];
	bool good[2];
	void init();
};
void Unit::init() {
	int i;
	scanf("%d", &id);
	for(i = 0; i < 2; i++) {
		char status;
		scanf("%d %c", &check[i], &status);
		if(status == 'Y') {
			good[i] = true;
		} else {
			good[i] = false;
		}
	}
}

int main()
{
	Unit unit[MAX];
	int t, T, i, j, k;
	int n;
	
	scanf("%d", &T);
	for(t = 0; t < T; t++) {
		scanf("%d", &n);
		for(i = 0; i < n; i++) {
			unit[i].init();
		}
		int faulty = -1;
		for(i = 0; i < n; i++) {
			bool maybe = true;
			for(j = 0; j < n && maybe; j++) {
				for(k = 0; i != j && k < 2 && maybe; k++) {
					if(unit[j].check[k] == unit[i].id && unit[j].good[k]) {
						maybe = false;
					} else if(unit[j].check[k] != unit[i].id && !unit[j].good[k]) {
						maybe = false;
					}
				}
			}
			if(maybe) {
				if(faulty == -1) {
					faulty = unit[i].id;
				} else {
					faulty = -1;
					break;
				}
			}
		}
		if(faulty == -1) {
			printf("impossible\n");
		} else {
			printf("%d\n", faulty);
		}
	}
	
	return 0;
}