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

namespace YukiCoderNo1
{
    class Program
    {
        private class RoadData
        {
            public int nextTown
            {
                get;
                private set;
            }
            public int cost
            {
                get;
                private set;
            }
            public int time
            {
                get;
                private set;
            }

            public RoadData(int nextTown, int cost, int time)
            {
                this.nextTown = nextTown;
                this.cost = cost;
                this.time = time;
            }
        }
        private static Dictionary<int, List<RoadData>> roadData = new Dictionary<int, List<RoadData>>();

        static void Main()
        {
            int targetTown = int.Parse(Console.ReadLine());
            int money = int.Parse(Console.ReadLine());
            int roadCount = int.Parse(Console.ReadLine());
            int[] townStart = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            int[] townEnd = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            int[] cost = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            int[] time = (Console.ReadLine()).Split(' ').Select(value => int.Parse(value)).ToArray();
            for (int i = 0; i < roadCount; i++)
            {
                roadData.Add(i, new List<RoadData>());
            }
            for (int i = 0; i < roadCount; i++)
            {
                roadData[townStart[i]].Add(new RoadData(townEnd[i], cost[i], time[i]));
            }
            List<int> timeList = GetTimeList(1, targetTown, money, 0);

            if (timeList.Count == 0) { timeList.Add(-1); }
            Console.WriteLine("{0}", timeList.Min());
        }
        private static List<int> GetTimeList(int nowTown, int targetTown, int nowMoney, int nowTime)
        {
            List<int> result = new List<int>();
            if (nowTown == targetTown)
            {
                result.Add(nowTime);
            }
            else
            {
                foreach (RoadData buffer in roadData[nowTown])
                {
                    if ((nowMoney - buffer.cost) >= 0)
                    {
                        result.AddRange(GetTimeList(buffer.nextTown, targetTown, (nowMoney - buffer.cost), (nowTime + buffer.time)));
                    }
                }
            }
            return result;
        }
    }
}