import java.util.*;

public class Main {
    static final int MOD = 1000000007;
    static ArrayList<HashMap<Integer, Integer>> graph = new ArrayList<>();
    static int[] sizes;
    static int n;
    static int x;
    static long sum = 0;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        int m = sc.nextInt();
        x = sc.nextInt();
        for (int i = 0; i < n; i++) {
            graph.add(new HashMap<>());
        }
        UnionFindTree uft = new UnionFindTree(n);
        for (int i = 0; i < m; i++) {
            int a = sc.nextInt() - 1;
            int b = sc.nextInt() - 1;
            int c = sc.nextInt();
            if (!uft.same(a, b)) {
                uft.unite(a, b);
                graph.get(a).put(b, c);
                graph.get(b).put(a, c);
            }
        }
        sizes = new int[n];
        getSize(0, 0);
        System.out.println(sum);
    }
    
    static int getSize(int idx, int parent) {
        sizes[idx] = 1;
        for (int y : graph.get(idx).keySet()) {
            if (y == parent) {
                continue;
            }
            int s = getSize(y, idx);
            sum += pow(x, graph.get(idx).get(y)) * (n - s) % MOD * s % MOD;
            sum %= MOD;
            sizes[idx] += s;
        }
        return sizes[idx];
    }
    
    static long pow(long x, int p) {
        if (p == 0) {
            return 1;
        } else if (p % 2 == 0) {
            return pow(x * x % MOD, p / 2);
        } else {
            return x * pow(x, p - 1) % MOD;
        }
    }
    
    static class UnionFindTree {
        int[] parents;
        
        public UnionFindTree(int size) {
            parents = new int[size];
            for (int i = 0; i < size; i++) {
                parents[i] = i;
            }
        }
        
        public int find(int a) {
            if (parents[a] == a) {
                return a;
            } else {
                return parents[a] = find(parents[a]);
            }
        }
        
        public boolean same(int a, int b) {
            return find(a) == find(b);
        }
        
        public void unite(int a, int b) {
            if (!same(a, b)) {
                parents[find(a)] = find(b);
            }
        }
    }
}