using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using SB = System.Text.StringBuilder;
using Number = System.Int64;
using C = System.Int32;
using V = System.Int32;
namespace Program
{
    public class Solver
    {
        public void Solve()
        {
            while (true)
            {
                var n = ri;
                var m = ri;
                var l = ri;
                if (n == 0) break;
                var g = Enumerate(n, x => new long[n]);
                for (int i = 0; i < n; i++)
                    for (int j = i + 1; j < n; j++)
                        g[i][j] = g[j][i] = INF;
                for (int i = 0; i < m; i++)
                {
                    var f = ri;
                    var t = ri;
                    var c = ri;
                    g[f][t] = g[t][f] = c;
                }
                for (int k = 0; k < n; k++)
                    for (int i = 0; i < n; i++)
                        for (int j = 0; j < n; j++)
                            g[i][j] = Math.Min(g[i][j], g[i][k] + g[k][j]);
                var G = new MaxFlow(2 * l + 2);
                var u = new int[l];
                var v = new int[l];
                var src = 2 * l;
                var sink = src + 1;
                for (int i = 0; i < l; i++)
                {
                    G.AddDirectedEdge(src, i, 1);
                    G.AddDirectedEdge(i + l, sink, 1);
                    u[i] = ri;
                    v[i] = ri;
                    for (int j = 0; j < i; j++)
                    {
                        if (v[j] + g[u[j]][u[i]] <= v[i]) G.AddDirectedEdge(j, i + l, 1);
                        if (v[i] + g[u[j]][u[i]] <= v[j]) G.AddDirectedEdge(i, j + l, 1);
                    }
                }
                //for (int i = 0; i < 2 * l + 2; i++) foreach (var e in G.G[i]) if (e.Cap != 0) IO.Printer.Out.WriteLine($"{i} {e.To} {e.Cost}");
                var mf = G.Execute(src, sink, INF);
                IO.Printer.Out.WriteLine(l - mf);
                //IO.Printer.Out.WriteLine("");

            }
        }

        const int INF = (int)1e9 + 1;
        //*
        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(System.Linq.Enumerable.ToArray(ie)); }
    //static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer: StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    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 = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != 0 && b != '-' && (b < '0' || '9' < b));
            if (b == 0) return long.MinValue;
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion

#region MaxFlow
public partial class MaxFlow
{
    public readonly List<Edge>[] G;
    readonly int[] lv, iter;
    public MaxFlow(int V)
    {
        G = new List<Edge>[V];
        lv = new int[V];
        iter = new int[V];
        for (int i = 0; i < G.Length; i++)
            G[i] = new List<Edge>();
    }

    public void AddDirectedEdge(int from, int to, C cap)
    {
        addEdge(from, to, cap, 0);
    }

    public void AddUndirectedEdge(int from, int to, C cap)
    {
        addEdge(from, to, cap, cap);
    }
    void addEdge(int f, int t, C c1, C c2)
    {
        var a = new Edge(t, c1);
        var b = new Edge(f, c2);
        Edge.Link(a, b);
        G[f].Add(a);
        G[t].Add(b);
    }


    public C Execute(int src, int sink, C f = -1)
    {
        C flow = 0;
        if (f < 0) f = C.MaxValue;
        while (f > 0)
        {
            bfs(src);
            if (lv[sink] == 0) return flow;
            Array.Clear(iter, 0, iter.Length);
            C df;
            while ((df = dfs(src, sink, f)) > 0) { flow += df; f -= df; }
        }
        return flow;
    }

    void bfs(int s)
    {
        Array.Clear(lv, 0, lv.Length);
        var q = new Queue<int>();
        lv[s] = 1;
        q.Enqueue(s);
        while (q.Count > 0)
        {
            var v = q.Dequeue();
            foreach (var e in G[v])
                if (e.Cap > 0 && lv[e.To] == 0)
                {
                    lv[e.To] = lv[v] + 1;
                    q.Enqueue(e.To);
                }
        }

    }
    C dfs(int v, int t, C f)
    {
        if (v == t) return f;
        C ret = 0;
        for (; iter[v] < G[v].Count; iter[v]++)
        {
            var e = G[v][iter[v]];
            if (e.Cap <= 0 || lv[v] >= lv[e.To]) continue;
            C df = dfs(e.To, t, Math.Min(f, e.Cap));
            if (df <= 0) continue;
            e.Cap -= df;
            e.Rev.Cap += df;
            ret += df; f -= df;
            if (f == 0) break;
        }
        return ret;

    }
}
public class Edge
{
    public static void Link(Edge e1, Edge e2)
    {
        e1.Rev = e2; e2.Rev = e1;
    }
    public int To { get; private set; }
    public Edge Rev { get; private set; }
    public C Cap { get; set; }
    public Edge(int t, C c)
    {
        To = t;
        Cap = c;
    }
    public override string ToString()
    {
        return string.Format("to: {0}, cap: {1}", To, Cap);
    }
}
#endregion

#region MinCostFlow
public class MinCostFlow
{
    bool hasng;
    public readonly List<Edge>[] G;
    public MinCostFlow(int V)
    {
        G = new List<Edge>[V];
        for (int i = 0; i < V; i++)
            G[i] = new List<Edge>();

    }
    public void AddDirectedEdge(int from, int to, C cap, V cost)
    {
        addEdge(from, to, cap, 0, cost);
    }

    public KeyValuePair<C, V> Execute(int src, int sink, C f = C.MaxValue, V inf = V.MaxValue / 2)
    {
        var n = G.Length;
        var dist = new V[n];
        var prev = new int[n];
        var prevEdge = new Edge[n];
        var potential = new V[n];


        C flow = 0;
        V cost = 0;
        var first = hasng;
        while (f > 0)
        {
            for (int i = 0; i < G.Length; i++)
                dist[i] = inf;

            //shortest path
            if (first)//spfa
            {
                var q = new Queue<int>();
                q.Enqueue(src); dist[src] = 0;
                var inQ = new bool[n];
                while (q.Count > 0)
                {
                    var p = q.Dequeue();
                    inQ[p] = false;
                    foreach (var e in G[p])
                    {
                        var t = e.To;
                        var d = dist[p] + e.Cost;
                        if (e.Cap > 0 && d < dist[t])
                        {
                            if (!inQ[t])
                            {
                                inQ[t] = true;
                                q.Enqueue(t);
                            }
                            dist[t] = d; prev[t] = p; prevEdge[t] = e;
                        }
                    }
                }
                first = false;
            }
            else//dijkstra
            {
                var vis = new bool[n];
                var pq = new PriorityQueue<KeyValuePair<int, V>>((l, r) => l.Value.CompareTo(r.Value));
                pq.Enqueue(new KeyValuePair<int, V>(src, 0));
                dist[src] = 0;
                while (pq.Count > 0)
                {
                    var p = pq.Dequeue().Key;
                    if (vis[p]) continue;
                    //Debug.WriteLine(p);
                    vis[p] = true;
                    foreach (var e in G[p])
                    {
                        if (e.Cap <= 0) continue;
                        var t = e.To;
                        if (vis[t]) continue;
                        var d = dist[p] + e.Cost + potential[p] - potential[t];
                        if (dist[t] > d)
                        {
                            dist[t] = d; prev[t] = p; prevEdge[t] = e;
                            pq.Enqueue(new KeyValuePair<int, V>(t, d));
                        }
                    }
                }


            }


            //update
            {
                if (dist[sink] == inf) break;
                for (int i = 0; i < n; i++)
                    potential[i] = Math.Min(inf, potential[i] + dist[i]);
                C df = f;
                V d = 0;
                for (var v = sink; v != src; v = prev[v])
                {
                    var e = prevEdge[v];
                    df = Math.Min(df, e.Cap); d += e.Cost;
                }
                if (d == 0) break;
                f -= df; cost += df * d; flow += df;
                for (var v = sink; v != src; v = prev[v])
                {
                    var e = prevEdge[v];
                    e.Cap -= df; e.Rev.Cap += df;
                }
            }

        }
        return new KeyValuePair<C, V>(flow, cost);
    }
    void addEdge(int f, int t, C c1, C c2, V e)
    {
        if (e < 0) hasng = true;
        var a = new Edge(t, c1, e);
        var b = new Edge(f, c2, -e);
        Edge.Link(a, b);
        G[f].Add(a);
        G[t].Add(b);
    }
    public class Edge
    {
        public static void Link(Edge e1, Edge e2)
        {
            e1.Rev = e2; e2.Rev = e1;
        }
        public int To { get; private set; }
        public Edge Rev { get; private set; }
        public V Cost { get; private set; }
        public C Cap { get; set; }
        public Edge(int t, C c, V e)
        {
            To = t;
            Cap = c;
            Cost = e;
        }
        public override string ToString()
        {
            return string.Format("to: {0}, cap: {1}", To, Cap);
        }
    }
}
#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: 75060