#include<cstdio>
#include<vector>
using namespace std;
const int maxn=100001;
int hashTable[maxn]={0};
struct Node{
    int address;
    char data;
    int next;
}node[maxn];
int main(){
    bool flag=false;
    int st1,st2,n,address,next;
    int arr1[maxn],arr2[maxn];
    char s;
    scanf("%d %d %d",&st1,&st2,&n);
    for(int i=0;i<n;i++){
        scanf("%d %c %d",&address,&s,&next);
        node[address].address=address;
        node[address].data=s;
        node[address].next=next;
    }
    int start1=st1,start2=st2,num;
    while(start1!=-1){
        hashTable[node[start1].address]=1;
        start1=node[start1].next;
    }
    while(start2!=-1){
        if(hashTable[node[start2].address]==1){
            num=node[start2].address;
            flag=true;
            break;
        }
        start2=node[start2].next;
    }
    if(flag==true)
        printf("%05d\n",num);
    else
        printf("-1\n");
    return 0;
}