import sys
sys.setrecursionlimit(10**6)
input=sys.stdin.readline

MOD=10**9+7

class UnionFind():
    def __init__(self,n):
        self.upper=[-1]*n

    def root(self,x):
        if self.upper[x]<0:
            return x
        else:
            self.upper[x]=self.root(self.upper[x])
            return self.upper[x]

    def equiv(self,x,y):
        return self.root(x)==self.root(y)

    def unite(self,x,y):
        x=self.root(x)
        y=self.root(y)
        if x==y:
            return
        if self.upper[x]>self.upper[y]:
            x,y=y,x
        self.upper[x]+=self.upper[y]
        self.upper[y]=x

N,M,X=map(int,input().split())
g=[[] for _ in range(N+1)]
uf=UnionFind(N+1)
for i in range(M):
    x,y,z=map(int,input().split())
    if not uf.equiv(x,y):
        g[x].append((y,pow(X,z,MOD)))
        g[y].append((x,pow(X,z,MOD)))
        uf.unite(x,y)

sz=[1]*(N+1)
ans=0

def dfs(v,p):
    global ans
    for dst,cost in g[v]:
        if dst==p:
            continue
        dfs(dst,v)
        ans+=sz[dst]*(N-sz[dst])%MOD*cost%MOD
        ans%=MOD
        sz[v]+=sz[dst]

dfs(1,-1)
print(ans)