Problem:
Score : 500 points

Problem Statement

There are N towns numbered 1 to N and M roads. The i-th road connects Town A_i and Town B_i bidirectionally and has a length of C_i.

Takahashi will travel between these towns by car, passing through these roads. The fuel tank of his car can contain at most L liters of fuel, and one liter of fuel is consumed for each unit distance traveled. When visiting a town while traveling, he can full the tank (or choose not to do so). Travel that results in the tank becoming empty halfway on the road cannot be done.

Process the following Q queries:

The tank is now full. Find the minimum number of times he needs to full his tank while traveling from Town s_i to Town t_i. If Town t_i is unreachable, print -1.

Constraints

All values in input are integers.

2 \leq N \leq 300

0 \leq M \leq \frac{N(N-1)}{2}

1 \leq L \leq 10^9

1 \leq A_i, B_i \leq N

A_i \neq B_i

\left(A_i, B_i\right) \neq \left(A_j, B_j\right) (if i \neq j)

\left(A_i, B_i\right) \neq \left(B_j, A_j\right) (if i \neq j)

1 \leq C_i \leq 10^9

1 \leq Q \leq N\left(N-1\right)

1 \leq s_i, t_i \leq N

s_i \neq t_i

\left(s_i, t_i\right) \neq \left(s_j, t_j\right) (if i \neq j)

Input

Input is given from Standard Input in the following format:

N M L
A_1 B_1 C_1
:
A_M B_M C_M
Q
s_1 t_1
:
s_Q t_Q

Output

Print Q lines.

The i-th line should contain the minimum number of times the tank needs to be fulled while traveling from Town s_i to Town t_i. If Town t_i is unreachable, the line should contain -1 instead.

Sample Input 1

3 2 5
1 2 3
2 3 3
2
3 2
1 3

Sample Output 1

0
1

To travel from Town 3 to Town 2, we can use the second road to reach Town 2 without fueling the tank on the way.

To travel from Town 1 to Town 3, we can first use the first road to get to Town 2, full the tank, and use the second road to reach Town 3.

Sample Input 2

4 0 1
1
2 1

Sample Output 2

-1

There may be no road at all.

Sample Input 3

5 4 4
1 2 2
2 3 2
3 4 3
4 5 2
20
2 1
3 1
4 1
5 1
1 2
3 2
4 2
5 2
1 3
2 3
4 3
5 3
1 4
2 4
3 4
5 4
1 5
2 5
3 5
4 5

Sample Output 3

0
0
1
2
0
0
1
2
0
0
0
1
1
1
0
0
2
2
1
0

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;

// (づ°ω°)づﾐe★゜・。。・゜゜・。。・゜☆゜・。。・゜゜・。。・゜
public class Solver
{
    public class Heap<T>
    {
        private readonly List<T> data;
        private readonly Comparison<T> compare;

        public Heap(Comparison<T> compare)
        {
            this.compare = compare;
            data = new List<T> { default(T) };
        }

        public int Count
        {
            get { return data.Count - 1; }
        }

        public T Peek()
        {
            return data[1];
        }

        public void Push(T item)
        {
            data.Add(item);
            var curPlace = Count;
            while (curPlace > 1 && compare(item, data[curPlace / 2]) < 0)
            {
                data[curPlace] = data[curPlace / 2];
                data[curPlace / 2] = item;
                curPlace /= 2;
            }
        }

        public T Pop()
        {
            var ret = data[1];
            data[1] = data[Count];
            data.RemoveAt(Count);
            var curPlace = 1;
            while (true)
            {
                var max = curPlace;
                if (Count >= curPlace * 2 && compare(data[max], data[2 * curPlace]) > 0)
                    max = 2 * curPlace;
                if (Count >= curPlace * 2 + 1 && compare(data[max], data[2 * curPlace + 1]) > 0)
                    max = 2 * curPlace + 1;
                if (max == curPlace)
                    break;
                var item = data[max];
                data[max] = data[curPlace];
                data[curPlace] = item;
                curPlace = max;
            }

            return ret;
        }
    }

    class Edge
    {
        public int to, weight;
        public Edge(int to, int weight)
        {
            this.to = to;
            this.weight = weight;
        }
    }

    int l;
    Tuple<int, int>[] Dijkstra(int start, List<Edge>[] edges)
    {
        int n = edges.Length;
        var dist = Enumerable.Repeat(Tuple.Create(1000, 0), n).ToArray();
        dist[start] = Tuple.Create(0, 0);

        var q = new Heap<Tuple<int, int, int>>((x, y) => (x.Item2 == y.Item2 ? x.Item3.CompareTo(y.Item3) : x.Item2.CompareTo(y.Item2)));
        q.Push(Tuple.Create(start, 0, 0));

        while (q.Count > 0)
        {
            var t = q.Pop();
            if (t.Item2 != dist[t.Item1].Item1 || t.Item3 != dist[t.Item1].Item2)
                continue;

            foreach (var e in edges[t.Item1])
            {
                int p = e.weight + t.Item3;
                int z = t.Item2;
                if (p > l)
                {
                    p = e.weight;
                    z++;
                }
                if (dist[e.to].Item1 == z && dist[e.to].Item2 > p || dist[e.to].Item1 > z)
                {
                    dist[e.to] = Tuple.Create(z, p);
                    q.Push(Tuple.Create(e.to, z, p));
                }
            }
        }

        return dist;
    }

    public void Solve()
    {
        int n = ReadInt();
        int m = ReadInt();
        l = ReadInt();

        var g = Init<List<Edge>>(n);
        for (int i = 0; i < m; i++)
        {
            int u = ReadInt() - 1;
            int v = ReadInt() - 1;
            int w = ReadInt();
            g[u].Add(new Edge(v, w));
            g[v].Add(new Edge(u, w));
        }

        var d = new Tuple<int, int>[n][];
        for (int i = 0; i < n; i++)
            d[i] = Dijkstra(i, g);

        for (int qq = ReadInt(); qq > 0; qq--)
        {
            int u = ReadInt() - 1;
            int v = ReadInt() - 1;
            if (d[u][v].Item1 == 1000)
                Write(-1);
            else
                Write(d[u][v].Item1);
        }
    }

    #region Main

    protected static TextReader reader;
    protected static TextWriter writer;
    static void Main()
    {
#if DEBUG
        reader = new StreamReader("..\\..\\input.txt");
        //reader = new StreamReader(Console.OpenStandardInput());
        writer = Console.Out;
        //writer = new StreamWriter("..\\..\\output.txt");
#else
        reader = new StreamReader(Console.OpenStandardInput());
        writer = new StreamWriter(Console.OpenStandardOutput());
        //reader = new StreamReader("input.txt");
        //writer = new StreamWriter("output.txt");
#endif
        try
        {
            new Solver().Solve();
            //var thread = new Thread(new Solver().Solve, 1024 * 1024 * 128);
            //thread.Start();
            //thread.Join();
        }
        catch (Exception ex)
        {
#if DEBUG
            Console.WriteLine(ex);
#else
            throw;
#endif
        }
        reader.Close();
        writer.Close();
    }

    #endregion

    #region Read / Write
    private static Queue<string> currentLineTokens = new Queue<string>();
    private static string[] ReadAndSplitLine() { return reader.ReadLine().Split(new[] { ' ', '\t', }, StringSplitOptions.RemoveEmptyEntries); }
    public static string ReadToken() { while (currentLineTokens.Count == 0)currentLineTokens = new Queue<string>(ReadAndSplitLine()); return currentLineTokens.Dequeue(); }
    public static int ReadInt() { return int.Parse(ReadToken()); }
    public static long ReadLong() { return long.Parse(ReadToken()); }
    public static double ReadDouble() { return double.Parse(ReadToken(), CultureInfo.InvariantCulture); }
    public static int[] ReadIntArray() { return ReadAndSplitLine().Select(int.Parse).ToArray(); }
    public static long[] ReadLongArray() { return ReadAndSplitLine().Select(long.Parse).ToArray(); }
    public static double[] ReadDoubleArray() { return ReadAndSplitLine().Select(s => double.Parse(s, CultureInfo.InvariantCulture)).ToArray(); }
    public static int[][] ReadIntMatrix(int numberOfRows) { int[][] matrix = new int[numberOfRows][]; for (int i = 0; i < numberOfRows; i++)matrix[i] = ReadIntArray(); return matrix; }
    public static int[][] ReadAndTransposeIntMatrix(int numberOfRows)
    {
        int[][] matrix = ReadIntMatrix(numberOfRows); int[][] ret = new int[matrix[0].Length][];
        for (int i = 0; i < ret.Length; i++) { ret[i] = new int[numberOfRows]; for (int j = 0; j < numberOfRows; j++)ret[i][j] = matrix[j][i]; } return ret;
    }
    public static string[] ReadLines(int quantity) { string[] lines = new string[quantity]; for (int i = 0; i < quantity; i++)lines[i] = reader.ReadLine().Trim(); return lines; }
    public static void WriteArray<T>(IEnumerable<T> array) { writer.WriteLine(string.Join(" ", array)); }
    public static void Write(params object[] array) { WriteArray(array); }
    public static void WriteLines<T>(IEnumerable<T> array) { foreach (var a in array)writer.WriteLine(a); }
    private class SDictionary<TKey, TValue> : Dictionary<TKey, TValue>
    {
        public new TValue this[TKey key]
        {
            get { return ContainsKey(key) ? base[key] : default(TValue); }
            set { base[key] = value; }
        }
    }
    private static T[] Init<T>(int size) where T : new() { var ret = new T[size]; for (int i = 0; i < size; i++)ret[i] = new T(); return ret; }
    #endregion
}