#include<bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i,m,n) for(int i=(m);i<(n);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define all(a) a.begin(),a.end()
#define rall(c) (c).rbegin(),(c).rend()
#define mp make_pair
#define endl '\n'
#define vec vector<ll>
#define mat vector<vector<ll> >
#define fi first
#define se second
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll> pll;
typedef long double ld;
typedef complex<double> comp;
const ll inf=1e9+7;
const ll mod=1e9+7;
const int MAX=200010;

//Union-Find木


int siz[MAX];
int par[MAX];
int depth[MAX];
void init(int n){
  for(int i=0;i<=n;i++){
      par[i]=i;
      depth[i]=0;
  }
  rep(i,n+1){
      siz[i]=1;
  }
}
int root(int x){
  return par[x]==x?x:par[x]=root(par[x]);
}
bool same(int x,int y){
  return root(x)==root(y);
}
void unite(int x,int y){
  x=root(x);
  y=root(y);
  ll sx=siz[x];
  ll sy=siz[y];
  if(x==y)return;
  if(depth[x]<depth[y]){
      par[x]=y;
  }else{
      par[y]=x;
      if(depth[x]==depth[y])depth[x]++;
  }
  siz[root(x)]=sx+sy;
}

ll rui(ll a,ll b){
    ll res=1;
    ll x=a;
    while(b){
        if(b&1)res=res*x%mod;
        b/=2;
        x=x*x%mod;
    }
    return res;
}
vector<vector<pll> >G(MAX);
vector<ll>sz(MAX);
void dfs(ll i,ll p){
    ll res=1;
    for(auto e:G[i]){
        if(e.fi==p)continue;
        dfs(e.fi,i);
        res+=sz[e.fi];
    }
    sz[i]=res;
}
ll n;
ll DFS(ll i,ll p){
    ll res=0;
    for(auto e:G[i]){
        if(e.fi==p)continue;
        res=(res+DFS(e.fi,i))%mod;
        res=(res+e.se*sz[e.fi]%mod*(n-sz[e.fi])%mod)%mod;
    }
    return res;
}
signed main(){
    ll m,x;cin>>n>>m>>x;
    init(n);
    rep(i,m){
        ll a,b,z;cin>>a>>b>>z;
        a--;b--;
        if(same(a,b))continue;
        ll v=rui(x,z);
        G[a].pb(mp(b,v));
        G[b].pb(mp(a,v));
        unite(a,b);
    }
    dfs(0,-1);
    ll ans=DFS(0,-1);
    if(ans<0)ans+=mod;
    cout<<ans<<endl;
}