import java.io.*;
import java.util.*;

public class fiber {
  public static void main(String[] args) { try {
    LineNumberReader Quelle = new LineNumberReader(new FileReader("fiber.in"));
    
    node[] nodes;
    
    while(true) {
      String Zeile = Quelle.readLine();
      if (Zeile==null) return;
      
      StringTokenizer Tokens = new StringTokenizer(Zeile);
      
      int anzahl = Integer.parseInt(Tokens.nextToken());
      
      if (anzahl==0) return;
      
      nodes = new node[anzahl+1];
      
      for (int i=1; i<=anzahl; i++) { 
      	nodes[i] = new node(anzahl, i);
	//System.out.println("added node "+i);
      }
              
      int source, target;
      String companies, route;
      int companymask=0;
      
      while (true) {
	Zeile = Quelle.readLine();
	if (Zeile==null) return;
	Tokens = new StringTokenizer(Zeile);
	source = Integer.parseInt(Tokens.nextToken());
	target = Integer.parseInt(Tokens.nextToken());
	
	//System.out.println("adding route from "+source+" to "+target);
	
	if ((source==0) && (target==0)) break;
	
	companies = Tokens.nextToken();
	nodes[source].addroute(companies,nodes[target]);
        
	for (int j=0; j<companies.length(); j++) {
	  int firmnumber = companies.charAt(j) - 'a';
	  //System.out.println("adding "+newfirms.charAt(j)+" as "+firmnumber);
	  companymask |= 1<<firmnumber;
	}
      }
          
      while (true) {
	Zeile = Quelle.readLine();
	route="";
	if (Zeile==null) return;
	Tokens = new StringTokenizer(Zeile);
	source = Integer.parseInt(Tokens.nextToken());
	target = Integer.parseInt(Tokens.nextToken());
	//System.out.print("testing route from "+source+" to "+target+": ");
	
	if ((source==0) && (target==0)) break;
	
	for (int i=0; i<26; i++) {
	  int cconmask = 1<<i;
	  if ((cconmask & companymask) != 0) {
	    if (nodes[source].findroute(cconmask,nodes[target])) {
	      //System.out.print("+"+i+"+");
	      route = route+(char)(i+'a');
	    }
	  }
	}
	
	if (route.equals("")) {
	  System.out.println('-');
	} else {
	  System.out.println(route);
	}
	
      }
      System.out.println();    
      //return;  
    }   
  } catch (Exception E) {System.out.println(E); E.printStackTrace();}}
}

class node {
  node[] Ziele;
  int[] companies;
  int anz;
  public boolean used=false;
  int nr;
   
  public node(int count, int number) {
    this.anz = count;
    Ziele = new node[anz];
    this.nr = number;
    companies = new int[anz];
  }  
  
  public void addroute(String newfirms, node target) {   
    int i;
    for (i=0; i<anz; i++) {
      if (Ziele[i]==null) {
      	Ziele[i] = target;
	break;
      } else if (Ziele[i] == target) {
	break;
      }
    }
    for (int j=0; j<newfirms.length(); j++) {
      int firmnumber = newfirms.charAt(j) - 'a';
      //System.out.println("adding "+newfirms.charAt(j)+" as "+firmnumber);
      companies[i] |= 1<<firmnumber;
    }
  }
  
  public boolean findroute(int compmask, node target) {
    //System.out.print("Searching comp"+company+" from "+nr+" to "+target.nr);
    
    if (this==target) return true;
    if (used) return false;
    boolean result;
    used = true;
    
    //System.out.println("compmask: "+compmask);
    
    for (int i=0; i<anz; i++) {
      if ((Ziele[i] != null) && (companies[i]&compmask) != 0) {
        //System.out.println("Testing target "+Ziele[i].nr+" with company "+company);
        result = Ziele[i].findroute(compmask, target);
	if (result) {
	  used = false;
	  return true;
	}	
      }
    }
    used = false;
    return false;
  }
}