PAT-A1032

#include<stdio.h>
struct pnode{
	int next;
	int flag;
}node[100010];
int main(){
int i, head1, head2, n, tp1, tp2, ans=-1;
char c;
scanf("%d%d%d",&head1,&head2,&n);
for(i=0;i<n;i++){
	scanf("%d %c %d",&tp1,&c,&tp2);
	node[tp1].next=tp2;
}
int p=head1;
while(p!=-1){
	node[p].flag=1;
	p=node[p].next;
}
p=head2;
while(p!=-1){
	if(node[p].flag==1){ans=p;break;}
	else p=node[p].next;
}
if(ans!=-1)printf("%05d\n",ans);
else printf("-1\n");
return 0;
}