#include <bits/stdc++.h>
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3fLL

using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef set<int> si;
typedef pair<int,int> ii;
typedef vector<ii> vii;
typedef map<string,int> msi;
typedef map<int,int> mi;

vector<pair<int,bitset<26> > > grafo[210];
bool vis[210];

bitset<26> dfs(int x,int y,bitset<26> e){
	vis[x] = true;
	if(x == y){
		vis[x]=false;
		return e;
	}
	bitset<26> ret;
	ret.reset();
	for(int i=0;i<grafo[x].size();i++){
		pair<int,bitset<26> > filho = grafo[x][i];
		if(!vis[filho.F]){

			bitset<26> s = e;
			s &= filho.S;//intersect

			s = dfs(filho.F,y,s);

			ret |= s;
		}
	}
	vis[x]=false;
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false); cin.tie(NULL);
	int n;
	while(cin >>n &&n){
		for(int i =1;i<=n;i++){
			grafo[i].clear();
		}
		int a,b;
		while(cin >> a >> b && a){
			string e;
			cin >>e;
			bitset<26> s;
			s.reset();
			for(int i =0;i<e.size();i++){
				s[e[i]-'a'] = 1;
			}
			grafo[a].pb(mp(b,s));
		}
		while(cin >> a >> b && a){
			memset(vis,0,sizeof vis);
			bitset<26> s;
			s.set();
			s = dfs(a,b,s);
			if(s.none()) cout << "-\n";
			else {
				for(int i=0;i<26;i++){
					if(s[i])cout<<(char)('a'+i);
				}
				cout<<'\n';
			}
		}
		cout<<'\n';

	}
	return 0;
}