#include <stdio.h>
#define MAXV 210
#define INF 10000000
int N;
int Edge[MAXV][MAXV];
int A[MAXV][MAXV];
void floyd()
{
	int i,j,k;
	for(i=0;i<N;i++)
		for(j=0;j<N;j++)
			A[i][j]=Edge[i][j];
	for(k=0;k<N;k++)
		for(i=0;i<N;i++)
			for(j=0;j<N;j++)
			{
				if(k==i||k==j)
					continue;
				A[i][j]=A[i][j]|(A[i][k]&A[k][j]);
			}
}
int main()
{
	int i,j,k;
	char str[30];
	char temp[30];
	int total;
	int u,v;
	while(scanf("%d",&N)!=EOF&&N)
	{
		for(i=0;i<N;i++)
			for(j=0;j<N;j++)
				Edge[i][j]=0;
		scanf("%d%d",&u,&v);
		while(1)
		{
			if(u==0&&v==0)
				break;
			u--;  v--;
			scanf("%s",str);
			i=0;
			while(str[i]!='\0')
			{
				Edge[u][v]=(Edge[u][v])|(1<<(str[i]-'a'));
				i++;
			}
			scanf("%d%d",&u,&v);
		}
		//printf("finished\n");
		floyd();
		scanf("%d%d",&u,&v);
		while(1)
		{
			if(u==0&&v==0)
				break;
			u--;  v--;
			k=0;
			total=0;
			while(k<26)
			{
				if(A[u][v]&1)
				{
					temp[total]=k+'a';
					total++;
				}
				A[u][v]=A[u][v]>>1;
				k++;
			}
			if(total==0)
				printf("-\n");
			else
			{
				k=0;
				while(k<total)
					printf("%c",temp[k++]);
				printf("\n");
			}
			scanf("%d%d",&u,&v);
		}
		printf("\n");
	}
	return 0;
}