#include<iostream>
#include<cassert>
using namespace std;

#define rep(i,n) for(int i=0;i<(n);i++)

using i64=long long;
int main(){

  int n, m, k; cin>> n>> m>> k;

  rep(_, m){
    int a, b; i64 c;
    cin>> a>> b>> c;
  }

  int prev=-1;
  rep(_, k){
    int i; cin>> i;
    assert(prev<i);
    prev=i;
  }

  cout<< -1<< endl;
  return 0;
}