using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using SB = System.Text.StringBuilder;
//using System.Numerics;
//using static System.Math;
namespace Program {
    public class Solver {
        //Random rnd = new Random();
        public void Solve() {
            for (; ; )
            {
                var n = ri; var m = ri;
                var cap = ri * 10;
                if (n == 0) return;
                var src = rs;
                var sink = rs;
                Debug.WriteLine(src);
                Debug.WriteLine(sink);
                var from = new string[n];
                var to = new string[n];
                var w = new int[n];
                for (int i = 0; i < n; i++)
                {
                    from[i] = rs;
                    to[i] = rs;
                    w[i] = ri;
                }
                var special = new string[m];
                for (int i = 0; i < m; i++)
                    special[i] = rs;
                var s = new List<string>() { src, sink };
                s.AddRange(from); s.AddRange(to); s.AddRange(special);
                s = s.Distinct().ToList();
                var f = from.Select(x => s.FindIndex(y => y == x)).ToArray();
                var t = to.Select(x => s.FindIndex(y => y == x)).ToArray();
                var sp = new bool[s.Count];
                foreach (var x in special)
                    sp[s.FindIndex(y => y == x)] = true;
                solve(s.Count,
                s.FindIndex(y => y == src),
                s.FindIndex(y => y == sink),
                f, t, w, cap, sp);
            }
        }
        void solve(int n, int src, int sink, int[] f, int[] t, int[] w, int c, bool[] sp) {
            var G = Enumerate(n, x => new List<KeyValuePair<int, int>>());
            for (int i = 0; i < f.Length; i++)
            {
                G[f[i]].Add(new KeyValuePair<int, int>(t[i], w[i]));
                G[t[i]].Add(new KeyValuePair<int, int>(f[i], w[i]));
            }
            var dist = new int[n, c + 1];
            for (int i = 0; i < n; i++)
                for (int j = 0; j <= c; j++)
                    dist[i, j] = 1000000000;
            dist[src, c] = 0;
            var pq = new PriorityQueue<KeyValuePair<int, int>>((l, r) => l.Value.CompareTo(r.Value));
            pq.Enqueue(new KeyValuePair<int, int>(src * 10000 + c, 0));
            while (pq.Any())
            {
                var p = pq.Dequeue();
                var pos = p.Key / 10000;
                var cap = p.Key % 10000;
                if (dist[pos, cap] < p.Value) continue;
                if (pos == sink)
                {
                    Console.WriteLine(p.Value); return;
                }
                //Debug.WriteLine($"{pos} {cap} {p.Value}");
                foreach (var e in G[pos])
                {
                    var to = e.Key;
                    var nc = cap - e.Value;
                    if (nc < 0) continue;
                    if (sp[to]) nc = c;
                    var nw = p.Value + e.Value;
                    if (nc >= 0 && dist[to, nc] > nw)
                    {
                        dist[to, nc] = nw;
                        pq.Enqueue(new KeyValuePair<int, int>(to * 10000 + nc, nw));

                    }
                }
            }
            Console.WriteLine(-1);

        }
        const long INF = 1L << 60;
        int ri { get { return sc.Integer(); } }
        long rl { get { return sc.Long(); } }
        double rd { get { return sc.Double(); } }
        string rs { get { return sc.Scan(); } }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());

        static T[] Enumerate<T>(int n, Func<int, T> f) {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f(i);
            return a;
        }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex {
    /*
    static public string AsString(this IEnumerable<char> ie) { return new string(ie.ToArray()); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") {
        return string.Join(st, ie);
    }*/
    static public void Main() {
        Console.SetOut(new Program.IO.Printer(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Program.Solver();
        solver.Solve();
        Console.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO {
    using System.IO;
    using System.Text;
    using System.Globalization;

    public class Printer: StreamWriter {
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
    }

    public class StreamScanner {
        public StreamScanner(Stream stream) { str = stream; }

        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }

        private byte read() {
            if (isEof) return 0;
            if (ptr >= len)
            {
                ptr = 0;
                if ((len = str.Read(buf, 0, 1024)) <= 0)
                {
                    isEof = true;
                    return 0;
                }
            }
            return buf[ptr++];
        }

        public char Char() {
            byte b = 0;
            do b = read(); while ((b < 33 || 126 < b) && !isEof);
            return (char)b;
        }
        public string Scan() {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine() {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n' && b != 0; b = (char)read()) if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long() { return isEof ? long.MinValue : long.Parse(Scan()); }
        public int Integer() { return isEof ? int.MinValue : int.Parse(Scan()); }
        public double Double() { return isEof ? double.NaN : double.Parse(Scan(), CultureInfo.InvariantCulture); }
    }
}

#endregion
#region BinaryHeap
public class PriorityQueue<T> {
    readonly List<T> heap = new List<T>();
    readonly Comparison<T> compare;
    public PriorityQueue() { compare = Comparer<T>.Default.Compare; }

    public PriorityQueue(Comparison<T> comparison) { compare = comparison; }
    public PriorityQueue(IComparer<T> comparer) { compare = comparer.Compare; }

    public void Enqueue(T item) {
        var pos = heap.Count;
        heap.Add(item);
        while (pos > 0)
        {
            var par = (pos - 1) / 2;
            if (compare(heap[par], item) <= 0)
                break;
            heap[pos] = heap[par];
            pos = par;
        }
        heap[pos] = item;

    }

    public T Dequeue() {
        var ret = heap[0];
        var pos = 0;
        var x = heap[heap.Count - 1];

        while (pos * 2 + 1 < heap.Count - 1)
        {
            var lch = pos * 2 + 1;
            var rch = pos * 2 + 2;
            if (rch < heap.Count - 1 && compare(heap[rch], heap[lch]) < 0) lch = rch;
            if (compare(heap[lch], x) >= 0)
                break;
            heap[pos] = heap[lch];
            pos = lch;
        }
        heap[pos] = x;
        heap.RemoveAt(heap.Count - 1);
        return ret;

    }
    public T Peek() { return heap[0]; }
    public int Count { get { return heap.Count; } }
    public bool Any() { return heap.Count > 0; }

    public T[] Items {
        get {
            var ret = heap.ToArray();
            Array.Sort(ret, compare);
            return ret;
        }
    }
}
#endregion


Measured memory_bytes: 77732