// letter by letter逐个字母 sublist子列表 suffixsuffix share共享
//Figure1图1

//To save some space, we may let the words share the same sublist if they share the same suffix.
//为了节省一些空间，如果单词共享相同的后缀，我们可以让它们共享相同的子列表

//the position of i in Figure1图1中i的位置

//You are supposed to find the starting position of the common suffix
//你需要找到共同后缀的起始位置
#include<iostream>

using namespace std;

const int N = 100010;

int n;
int h1,h2,ne[N],st[N];
char e[N];

int main()
{
    cin>>h1>>h2>>n;
    for(int i = 0; i<n; i++)
    {
        int address,next;
        char data;
        cin>>address>>data>>next;
        e[address] = data,ne[address] = next;
    }
    //遍历链表
    for(int i = h1; i!=-1; i = ne[i])
        st[i] = true;
    for(int i = h2; i!=-1; i = ne[i])
        if(st[i])//如果链表1出现过
        {
            printf("%05d\n",i);
            return 0;
        }
    puts("-1");
    return 0;
}