Problem:
Score : 900 points

Problem Statement

We have an undirected weighted graph with N vertices and M edges.
The i-th edge in the graph connects Vertex U_i and Vertex V_i, and has a weight of W_i.
Additionally, you are given an integer X.

Find the number of ways to paint each edge in this graph either white or black such that the following condition is met, modulo 10^9 + 7:

The graph has a spanning tree that contains both an edge painted white and an edge painted black. Furthermore, among such spanning trees, the one with the smallest weight has a weight of X.

Here, the weight of a spanning tree is the sum of the weights of the edges contained in the spanning tree.

Constraints

1 \leq N \leq 1 000

1 \leq M \leq 2 000

1 \leq U_i, V_i \leq N (1 \leq i \leq M)

1 \leq W_i \leq 10^9 (1 \leq i \leq M)

If i \neq j, then (U_i, V_i) \neq (U_j, V_j) and (U_i, V_i) \neq (V_j, U_j).

U_i \neq V_i (1 \leq i \leq M)

The given graph is connected.

1 \leq X \leq 10^{12}

All input values are integers.

Input

Input is given from Standard Input in the following format:

N M
X
U_1 V_1 W_1
U_2 V_2 W_2
:
U_M V_M W_M

Output

Print the answer.

Sample Input 1

3 3
2
1 2 1
2 3 1
3 1 1

Sample Output 1

6

Sample Input 2

3 3
3
1 2 1
2 3 1
3 1 2

Sample Output 2

2

Sample Input 3

5 4
1
1 2 3
1 3 3
2 4 6
2 5 8

Sample Output 3

0

Sample Input 4

8 10
49
4 6 10
8 4 11
5 8 9
1 8 10
3 8 128773450
7 8 10
4 2 4
3 4 1
3 1 13
5 2 2

Sample Output 4

4

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
class Solve{
    public Solve(){}
    StringBuilder sb;
    ReadData re;
    public static int Main(){
        new Solve().Run();
        return 0;
    }
    void Run(){
        sb = new StringBuilder();
        re = new ReadData();
        Calc();
        Console.Write(sb.ToString());
    }
    void Calc(){
        Fact F = new Fact(10000);
        long[] TT = new long[10000];
        TT[0] = 1;
        for(int i=1;i<=9999;i++){
            TT[i] = TT[i-1] * 2 % Define.mod;
        }
        int N = re.i();
        int M = re.i();
        long X = re.l();
        Edge[] E = new Edge[M];
        for(int i=0;i<M;i++){
            E[i] = new Edge(re.i()-1,re.i()-1,re.l());
        }
        Array.Sort(E,(x,y)=>(x.c - y.c > 0 ? 1 : (x.c == y.c ? 0 : -1)));
        bool[] used = new bool[M];
        UnionFind U = new UnionFind(N);
        long cost = 0;
        for(int i=0;i<M;i++){
            if(!U.Same(E[i].f,E[i].t)){
                used[i] = true;
                U.Union(E[i].f,E[i].t);
                cost += E[i].c;
            }
        }
        long count = 0;
        if(cost == X){
            count = (TT[N-1]+Define.mod-2) % Define.mod * TT[M-N+1] % Define.mod;
        }
        long[] costs = new long[M];
        for(int i=0;i<M;i++){
            if(!used[i]){
                long costi = E[i].c;
                UnionFind Ui = new UnionFind(N);
                Ui.Union(E[i].f,E[i].t);
                int unneed = -1;
                for(int j=0;j<M;j++){
                    if(!Ui.Same(E[j].f,E[j].t)){
                        Ui.Union(E[j].f,E[j].t);
                        costi += E[j].c;
                    }
                    else if(used[j]){
                        unneed = j;
                    }
                }
                costs[i] = costi;
            }
        }
        for(int i=0;i<M;i++){
            if(costs[i] == X){
                int cc = 0;
                for(int j=0;j<M;j++){
                    if(costs[j] < costs[i] || (costs[j] == costs[i] && j <= i)){
                        cc++;
                    }
                }
                count += TT[M-cc+1] % Define.mod;
                count %= Define.mod;
            }
        }
        sb.Append(count+"\n");
    }
}
struct Edge{
    public int f;
    public int t;
    public long c;
    public Edge(int f0,int t0,long c0){
        f = f0;
        t = t0;
        c = c0;
    }
}
class UnionFind{
    int[] par;
    public UnionFind(int n){
        par = new int[n];
        for(int i=0;i<n;i++){
            par[i] = i;
        }
    }
    public void Union(int x,int y){
        par[Get(x)] = Get(y); 
    }
    public bool Same(int x,int y){
        return Get(x) == Get(y);
    }
    int Get(int x){
        if(x != par[x]){
            par[x] = Get(par[x]);
        }
        return par[x];
    }
}
class Fact{
    public long[] f;
    public long[] rf;
    public Fact(int N){
        f = new long[N+1];
        rf = new long[N+1];
        for(int i=0;i<N+1;i++){
            if(i == 0){
                f[i] = 1;
            }
            else{
                f[i] = (f[i-1]*i)%Define.mod;
            }
        }
        for(int i=N;i>=0;i--){
            if(i == N){
                rf[i] = pow(f[N],Define.mod-2);
            }
            else{
                rf[i] = rf[i+1]*(i+1)%Define.mod;
            }
        }
    }
    public long pow(long N,long K){
        if(K == 0){
            return 1;
        }
        else if(K % 2 == 0){
            long t = pow(N,K/2);
            return t*t%Define.mod;
        }
        else{
            return N*pow(N,K-1)%Define.mod;
        }
    }
    public long GetFact(int N){
        return f[N];
    }
    public long GetConv(int N,int R){
        return ((f[N]*rf[R])%Define.mod*rf[N-R])%Define.mod;
    }
}
class ReadData{
    string[] str;
    int counter;
    public ReadData(){
        counter = 0;
    }
    public string s(){
        if(counter == 0){
            str = Console.ReadLine().Split(' ');
            counter = str.Length;
        }
        counter--;
        return str[str.Length-counter-1];
    }
    public int i(){
        return int.Parse(s());
    }
    public long l(){
        return long.Parse(s());
    }
    public double d(){
        return double.Parse(s());
    }
    public int[] ia(int N){
        int[] ans = new int[N];
        for(int j=0;j<N;j++){
            ans[j] = i();
        }
        return ans;
    }
    public int[] ia(){
        str = Console.ReadLine().Split(' ');
        counter = 0;
        int[] ans = new int[str.Length];
        for(int j=0;j<str.Length;j++){
            ans[j] = int.Parse(str[j]);
        }
        return ans;
    }
    public long[] la(int N){
        long[] ans = new long[N];
        for(int j=0;j<N;j++){
            ans[j] = l();
        }
        return ans;
    }
    public long[] la(){
        str = Console.ReadLine().Split(' ');
        counter = 0;
        long[] ans = new long[str.Length];
        for(int j=0;j<str.Length;j++){
            ans[j] = long.Parse(str[j]);
        }
        return ans;
    }
    public double[] da(int N){
        double[] ans = new double[N];
        for(int j=0;j<N;j++){
            ans[j] = d();
        }
        return ans;
    }
    public double[] da(){
        str = Console.ReadLine().Split(' ');
        counter = 0;
        double[] ans = new double[str.Length];
        for(int j=0;j<str.Length;j++){
            ans[j] = double.Parse(str[j]);
        }
        return ans;
    }
    public List<int>[] g(int N,int[] f,int[] t){
        List<int>[] ans = new List<int>[N];
        for(int j=0;j<N;j++){
            ans[j] = new List<int>();
        }
        for(int j=0;j<f.Length;j++){
            ans[f[j]].Add(t[j]);
            ans[t[j]].Add(f[j]);
        }
        return ans;
    }
    public List<int>[] g(int N,int M){
        List<int>[] ans = new List<int>[N];
        for(int j=0;j<N;j++){
            ans[j] = new List<int>();
        }
        for(int j=0;j<M;j++){
            int f = i()-1;
            int t = i()-1;
            ans[f].Add(t);
            ans[t].Add(f);
        }
        return ans;
    }
    public List<int>[] g(){
        int N = i();
        int M = i();
        List<int>[] ans = new List<int>[N];
        for(int j=0;j<N;j++){
            ans[j] = new List<int>();
        }
        for(int j=0;j<M;j++){
            int f = i()-1;
            int t = i()-1;
            ans[f].Add(t);
            ans[t].Add(f);
        }
        return ans;
    }
}
public static class Define{
    public const long mod = 1000000007;
}
public static class Debug{
    public static void Print(double[,,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                for(int l=0;l<k.GetLength(2);l++){
                    Console.Write(k[i,j,l]+" ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
    public static void Print(double[,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                Console.Write(k[i,j]+" ");
            }
            Console.WriteLine();
        }
    }
    public static void Print(double[] k){
        for(int i=0;i<k.Length;i++){
            Console.WriteLine(k[i]);
        }
    }
    public static void Print(long[,,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                for(int l=0;l<k.GetLength(2);l++){
                    Console.Write(k[i,j,l]+" ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
    public static void Print(long[,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                Console.Write(k[i,j]+" ");
            }
            Console.WriteLine();
        }
    }
    public static void Print(long[] k){
        for(int i=0;i<k.Length;i++){
            Console.WriteLine(k[i]);
        }
    }
    public static void Print(int[,,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                for(int l=0;l<k.GetLength(2);l++){
                    Console.Write(k[i,j,l]+" ");
                }
                Console.WriteLine();
            }
            Console.WriteLine();
        }
    }
    public static void Print(int[,] k){
        for(int i=0;i<k.GetLength(0);i++){
            for(int j=0;j<k.GetLength(1);j++){
                Console.Write(k[i,j]+" ");
            }
            Console.WriteLine();
        }
    }
    public static void Print(int[] k){
        for(int i=0;i<k.Length;i++){
            Console.WriteLine(k[i]);
        }
    }
}