/*
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......
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