using System;
using System.Collections.Generic;
using System.Linq;

namespace YukiCoderNo1
{
    class Program
    {
        private static int[] townStart = new int[0];
        private static int[] townEnd = new int[0];
        private static int[] cost = new int[0];
        private static int[] time = new int[0];
        private static int roadCount = 0;
        private static int targetTown = 0;
        private static int money = 0;
        static void Main()
        {
            targetTown = int.Parse(Console.ReadLine());
            money = int.Parse(Console.ReadLine());
            roadCount = int.Parse(Console.ReadLine());
            townStart = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            townEnd = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            cost = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            time = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            List<int> timeList = GetTimeList(1, money, 0);

            if (timeList.Count == 0) { timeList.Add(-1); }
            Console.WriteLine("{0}", timeList.Min());
        }
        private static List<int> GetTimeList(int nowTown, int nowMoney, int nowTime)
        {
            List<int> result = new List<int>();
            if (nowTown == targetTown)
            {
                result.Add(nowTime);
            }
            else
            {
                for (int i = 0; i < roadCount; i++)
                {
                    if (townStart[i] == nowTown)
                    {
                        if ((nowMoney - cost[i]) >= 0)
                        {
                            result.AddRange(GetTimeList(townEnd[i], (nowMoney - cost[i]), (nowTime + time[i])));
                        }
                    }
                }
            }
            return result;
        }
    }
}