import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

class UnionFind:
	def __init__(self, n):
		self.par = [i for i in range(n + 1)]
		self.rank = [0] * (n + 1)

	def find(self, x):
		if self.par[x] == x:
			return x
		else:
			self.par[x] = self.find(self.par[x])
			return self.par[x]

	def same_check(self, x, y):
		return self.find(x) == self.find(y)

	def union(self, x, y):
		x = self.find(x); y = self.find(y)
		if self.rank[x] < self.rank[y]:
			self.par[x] = y
		else:
			self.par[y] = x
			if self.rank[x] == self.rank[y]:
				self.rank[x] += 1


class Graph(object):
	def __init__(self):
		self.graph = defaultdict(list)

	def __len__(self):
		return len(self.graph)

	def add_edge(self, a, b):
		self.graph[a].append(b)


ans = 0
def DFS(N, G, W, visit, node, D, X):
	for i in G.graph[node]:
		if visit[i] != 1:
			visit[i] = 1
			DFS(N, G, W, visit, i, D, X)
			W[node] += W[i]
			global ans
			ans += ((N - W[i]) * W[i] * pow(X, D[(10 ** 6) * node + i], con)) % con
			ans %= con

#処理内容
def main():
	N, M, X = getlist()
	UF = UnionFind(N)
	D = defaultdict(int)
	G = Graph()
	for i in range(M):
		x, y, z = getlist()
		x -= 1; y -= 1
		# x, y = list(sorted([x, y]))
		if not UF.same_check(x, y):
			UF.union(x, y)
			G.add_edge(x, y)
			G.add_edge(y, x)
			D[(10 ** 6) * x + y] = z
			D[(10 ** 6) * y + x] = z

	W = [1] * N
	visit = [0] * N
	visit[0] = 1
	DFS(N, G, W, visit, 0, D, X)
	print(ans)

if __name__ == '__main__':
	main()