学步园

/*
notice that num[a]=b and num[a]=c won't happen;
*/
#include<stdio.h>
int num[100000],flag[100000];
int main(){
	int i,j,n;
	int sa,sb;
	scanf("%d %d %d",&sa,&sb,&n);
	int ta,tb;
	char tc;
	for(i=0;i<100000;i++){
		flag[i]=0;
	}
	for(i=0;i<n;i++){
		scanf("%d %c %d",&ta,&tc,&tb);
		num[ta]=tb;
	}
	while(sa!=-1){
		flag[sa]=1;
		sa=num[sa];
	}
	while(sb!=-1){
		if(flag[sb]) break;	
		else sb=num[sb];	
	}
	if(sb==-1) printf("-1\n");
	else printf("%05d\n",sb);
	return 0; 
}