import java.io.*;
import java.util.*;

public class Main {
    static int n;
    static ArrayList<ArrayList<Path>> graph = new ArrayList<>();
    static int x;
    static long ans = 0;
    static final int MOD = 1000000007;
    static HashMap<Integer, Long> dp = new HashMap<>();
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        n = sc.nextInt();
        int m = sc.nextInt();
        x = sc.nextInt();
        for (int i = 0; i < n; i++) {
            graph.add(new ArrayList<>());
        }
        UnionFindTree uft = new UnionFindTree(n);
        for (int i = 0; i < m; i++) {
            int left = sc.nextInt() - 1;
            int right = sc.nextInt() - 1;
            int cost = sc.nextInt();
            if (uft.same(left, right)) {
                continue;
            }
            uft.unite(left, right);
            graph.get(left).add(new Path(right, cost));
            graph.get(right).add(new Path(left, cost));
        }
        getCount(0, 0);
        System.out.println(ans);
    }
    
    static long getCount(int idx, int p) {
        long count = 1;
        for (Path y : graph.get(idx)) {
            if (y.idx == p) {
                continue;
            }
            long tmp = getCount(y.idx, idx);
            ans += (n - tmp) * tmp % MOD * pow(x, y.value) % MOD;
            ans %= MOD;
            count += tmp;
        }
        return count;
    }
    
    static long pow(long x, int p) {
        if (dp.containsKey(p)) {
            return dp.get(p);
        }
        long ans;
        if (p == 0) {
            ans = 1;
        } else if(p % 2 == 0) {
            ans = pow(x, p / 2) * pow(x, p / 2) % MOD;
        } else {
            ans = pow(x, p - 1) * x % MOD;
        }
        dp.put(p, ans);
        return ans;
    }
    
    static class Path {
        int idx;
        int value;
        
        public Path(int idx, int value) {
            this.idx = idx;
            this.value = value;
        }
    }
    static class UnionFindTree {
        int[] parent;
        
        public UnionFindTree(int size) {
            parent = new int[size];
            for (int i = 0; i < size; i++) {
                parent[i] = i;
            }
        }
        
        public int find(int x) {
            if (parent[x] == x) {
                return x;
            } else {
                return parent[x] = find(parent[x]);
            }
        }
        
        public boolean same(int x, int y) {
            return find(x) == find(y);
        }
        
        public void unite(int x, int y) {
            if (!same(x, y)) {
                parent[find(x)] = find(y);
            }
        }
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}