#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
#define MD (1000000007U)
void *wmem;
char memarr[96000000];
template<class T> inline void walloc1d(T **arr, int x, void **mem = &wmem){
  static int skip[16] = {0, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  (*mem) = (void*)( ((char*)(*mem)) + skip[((unsigned long long)(*mem)) & 15] );
  (*arr)=(T*)(*mem);
  (*mem)=((*arr)+x);
}
struct Modint{
  unsigned val;
  Modint(){
    val=0;
  }
  Modint(int a){
    val = ord(a);
  }
  Modint(unsigned a){
    val = ord(a);
  }
  Modint(long long a){
    val = ord(a);
  }
  Modint(unsigned long long a){
    val = ord(a);
  }
  inline unsigned ord(unsigned a){
    return a%MD;
  }
  inline unsigned ord(int a){
    a %= (int)MD;
    if(a < 0){
      a += MD;
    }
    return a;
  }
  inline unsigned ord(unsigned long long a){
    return a%MD;
  }
  inline unsigned ord(long long a){
    a %= (int)MD;
    if(a < 0){
      a += MD;
    }
    return a;
  }
  inline unsigned get(){
    return val;
  }
  inline Modint &operator+=(Modint a){
    val += a.val;
    if(val >= MD){
      val -= MD;
    }
    return *this;
  }
  inline Modint &operator-=(Modint a){
    if(val < a.val){
      val = val + MD - a.val;
    }
    else{
      val -= a.val;
    }
    return *this;
  }
  inline Modint &operator*=(Modint a){
    val = ((unsigned long long)val*a.val)%MD;
    return *this;
  }
  inline Modint &operator/=(Modint a){
    return *this *= a.inverse();
  }
  inline Modint operator+(Modint a){
    return Modint(*this)+=a;
  }
  inline Modint operator-(Modint a){
    return Modint(*this)-=a;
  }
  inline Modint operator*(Modint a){
    return Modint(*this)*=a;
  }
  inline Modint operator/(Modint a){
    return Modint(*this)/=a;
  }
  inline Modint operator+(int a){
    return Modint(*this)+=Modint(a);
  }
  inline Modint operator-(int a){
    return Modint(*this)-=Modint(a);
  }
  inline Modint operator*(int a){
    return Modint(*this)*=Modint(a);
  }
  inline Modint operator/(int a){
    return Modint(*this)/=Modint(a);
  }
  inline Modint operator+(long long a){
    return Modint(*this)+=Modint(a);
  }
  inline Modint operator-(long long a){
    return Modint(*this)-=Modint(a);
  }
  inline Modint operator*(long long a){
    return Modint(*this)*=Modint(a);
  }
  inline Modint operator/(long long a){
    return Modint(*this)/=Modint(a);
  }
  inline Modint operator-(void){
    Modint res;
    if(val){
      res.val=MD-val;
    }
    else{
      res.val=0;
    }
    return res;
  }
  inline operator bool(void){
    return val!=0;
  }
  inline operator int(void){
    return get();
  }
  inline operator long long(void){
    return get();
  }
  inline Modint inverse(){
    int a = val;
    int b = MD;
    int u = 1;
    int v = 0;
    int t;
    Modint res;
    while(b){
      t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    if(u < 0){
      u += MD;
    }
    res.val = u;
    return res;
  }
  inline Modint pw(unsigned long long b){
    Modint a(*this);
    Modint res;
    res.val = 1;
    while(b){
      if(b&1){
        res *= a;
      }
      b >>= 1;
      a *= a;
    }
    return res;
  }
  inline bool operator==(int a){
    return ord(a)==val;
  }
  inline bool operator!=(int a){
    return ord(a)!=val;
  }
}
;
inline Modint operator+(int a, Modint b){
  return Modint(a)+=b;
}
inline Modint operator-(int a, Modint b){
  return Modint(a)-=b;
}
inline Modint operator*(int a, Modint b){
  return Modint(a)*=b;
}
inline Modint operator/(int a, Modint b){
  return Modint(a)/=b;
}
inline Modint operator+(long long a, Modint b){
  return Modint(a)+=b;
}
inline Modint operator-(long long a, Modint b){
  return Modint(a)-=b;
}
inline Modint operator*(long long a, Modint b){
  return Modint(a)*=b;
}
inline Modint operator/(long long a, Modint b){
  return Modint(a)/=b;
}
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
inline void wt_L(int x){
  int s=0;
  int m=0;
  char f[10];
  if(x<0){
    m=1;
    x=-x;
  }
  while(x){
    f[s++]=x%10;
    x/=10;
  }
  if(!s){
    f[s++]=0;
  }
  if(m){
    my_putchar_unlocked('-');
  }
  while(s--){
    my_putchar_unlocked(f[s]+'0');
  }
}
inline void wt_L(Modint x){
  int i;
  i = (int)x;
  wt_L(i);
}
template<class T, class S> inline T pow_L(T a, S b){
  T res = 1;
  res = 1;
  for(;;){
    if(b&1){
      res *= a;
    }
    b >>= 1;
    if(b==0){
      break;
    }
    a *= a;
  }
  return res;
}
inline double pow_L(double a, double b){
  return pow(a,b);
}
template<class S> inline void arrInsert(const int k, int &sz, S a[], const S aval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  a[k] = aval;
}
template<class S, class T> inline void arrInsert(const int k, int &sz, S a[], const S aval, T b[], const T bval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  for(i=sz-1;i>k;i--){
    b[i] = b[i-1];
  }
  a[k] = aval;
  b[k] = bval;
}
template<class S, class T, class U> inline void arrInsert(const int k, int &sz, S a[], const S aval, T b[], const T bval, U c[], const U cval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  for(i=sz-1;i>k;i--){
    b[i] = b[i-1];
  }
  for(i=sz-1;i>k;i--){
    c[i] = c[i-1];
  }
  a[k] = aval;
  b[k] = bval;
  c[k] = cval;
}
template<class S, class T, class U, class V> inline void arrInsert(const int k, int &sz, S a[], const S aval, T b[], const T bval, U c[], const U cval, V d[], const V dval){
  int i;
  sz++;
  for(i=sz-1;i>k;i--){
    a[i] = a[i-1];
  }
  for(i=sz-1;i>k;i--){
    b[i] = b[i-1];
  }
  for(i=sz-1;i>k;i--){
    c[i] = c[i-1];
  }
  for(i=sz-1;i>k;i--){
    d[i] = d[i-1];
  }
  a[k] = aval;
  b[k] = bval;
  c[k] = cval;
  d[k] = dval;
}
struct unionFind{
  int *d;
  int N;
  int M;
  inline void malloc(const int n){
    d = (int*)std::malloc(n*sizeof(int));
    M = n;
  }
  inline void malloc(const int n, const int fg){
    d = (int*)std::malloc(n*sizeof(int));
    M = n;
    if(fg){
      init(n);
    }
  }
  inline void free(void){
    std::free(d);
  }
  inline void walloc(const int n, void **mem=&wmem){
    walloc1d(&d, n, mem);
    M = n;
  }
  inline void walloc(const int n, const int fg, void **mem=&wmem){
    walloc1d(&d, n, mem);
    M = n;
    if(fg){
      init(n);
    }
  }
  inline void init(const int n){
    int i;
    N = n;
    for(i=(0);i<(n);i++){
      d[i] = -1;
    }
  }
  inline void init(void){
    init(M);
  }
  inline int get(int a){
    int t = a;
    int k;
    while(d[t]>=0){
      t=d[t];
    }
    while(d[a]>=0){
      k=d[a];
      d[a]=t;
      a=k;
    }
    return a;
  }
  inline int connect(int a, int b){
    if(d[a]>=0){
      a=get(a);
    }
    if(d[b]>=0){
      b=get(b);
    }
    if(a==b){
      return 0;
    }
    if(d[a] < d[b]){
      d[a] += d[b];
      d[b] = a;
    }
    else{
      d[b] += d[a];
      d[a] = b;
    }
    return 1;
  }
  inline int operator()(int a){
    return get(a);
  }
  inline int operator()(int a, int b){
    return connect(a,b);
  }
  inline int& operator[](const int a){
    return d[a];
  }
  inline int size(int a){
    a = get(a);
    return -d[a];
  }
  inline int sizeList(int res[]){
    int i;
    int sz=0;
    for(i=(0);i<(N);i++){
      if(d[i]<0){
        res[sz++] = -d[i];
      }
    }
    return sz;
  }
}
;
struct graph{
  int N;
  int *es;
  int **edge;
  void setEdge(int N__, int M, int A[], int B[], void **mem = &wmem){
    int i;
    N = N__;
    walloc1d(&es, N, mem);
    walloc1d(&edge, N, mem);
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      es[A[i]]++;
      es[B[i]]++;
    }
    for(i=(0);i<(N);i++){
      walloc1d(&edge[i], es[i], mem);
    }
    for(i=(0);i<(N);i++){
      es[i] = 0;
    }
    for(i=(0);i<(M);i++){
      edge[A[i]][es[A[i]]++] = B[i];
      edge[B[i]][es[B[i]]++] = A[i];
    }
  }
  void getDist(int root, int res[], void *mem = wmem){
    int i;
    int j;
    int k;
    int*q;
    int s;
    int z;
    walloc1d(&q, N, &mem);
    for(i=(0);i<(N);i++){
      res[i]=-1;
    }
    res[root]=0;
    s=0;
    z=1;
    q[0]=root;
    while(z){
      i=q[s++];
      z--;
      for(j=(0);j<(es[i]);j++){
        k=edge[i][j];
        if(res[k]>=0){
          continue;
        }
        res[k]=res[i]+1;
        q[s+z++]=k;
      }
    }
  }
  void SubTreeSize(int root, int res[], void *mem = wmem){
    int i;
    int j;
    int k;
    int m;
    int *q;
    int qs = 0;
    int qe = 1;
    walloc1d(&q,N,&mem);
    for(i=(0);i<(N);i++){
      res[i] = -1;
    }
    res[root] = 0;
    q[0] = root;
    while(qs < qe){
      i = q[qs++];
      for(j=(0);j<(es[i]);j++){
        k = edge[i][j];
        if(res[k]==0){
          continue;
        }
        res[k] = 0;
        q[qe++] = k;
      }
    }
    for(m=(N)-1;m>=(0);m--){
      i = q[m];
      res[i] = 1;
      for(j=(0);j<(es[i]);j++){
        k = edge[i][j];
        res[i] += res[k];
      }
    }
  }
}
;
int N;
int M;
int X;
int A[200000];
int B[200000];
int Z[200000];
graph g;
int sz[200000];
int dep[200000];
int main(){
  wmem = memarr;
  int i;
  int j;
  int k = 0;
  unionFind uf;
  Modint res = 0;
  rd(N);
  rd(M);
  rd(X);
  {
    int Lj4PdHRW;
    for(Lj4PdHRW=(0);Lj4PdHRW<(M);Lj4PdHRW++){
      rd(A[Lj4PdHRW]);A[Lj4PdHRW] += (-1);
      rd(B[Lj4PdHRW]);B[Lj4PdHRW] += (-1);
      rd(Z[Lj4PdHRW]);
    }
  }
  uf.malloc(N, 1);
  for(i=(0);i<(M);i++){
    if(uf(A[i],B[i])){
      arrInsert(k, k, A, A[i], B, B[i], Z, Z[i]);
    }
  }
  g.setEdge(N, N-1, A, B);
  g.SubTreeSize(0, sz);
  g.getDist(0, dep);
  for(i=(0);i<(N-1);i++){
    if(dep[A[i]] < dep[B[i]]){
      swap(A[i], B[i]);
    }
    res += ((pow_L(Modint(X),Z[i]))) * sz[A[i]] * (N-sz[A[i]]);
  }
  wt_L(res);
  wt_L('\n');
  return 0;
}
// cLay varsion 20200813-1 [beta]

// --- original code ---
// int N, M, X, A[2d5], B[2d5], Z[2d5];
// graph g;
// int sz[2d5], dep[2d5];
// {
//   int i, j, k = 0;
//   unionFind uf;
//   Modint res = 0;
//   rd(N,M,X,(A--,B--,Z)(M));
//   uf.malloc(N, 1);
//   rep(i,M) if(uf(A[i],B[i])) arrInsert(k, k, A, A[i], B, B[i], Z, Z[i]);
// 
//   g.setEdge(N, N-1, A, B);
//   g.SubTreeSize(0, sz);
//   g.getDist(0, dep);
// 
//   rep(i,N-1){
//     if(dep[A[i]] < dep[B[i]]) swap(A[i], B[i]);
//     res += (Modint(X) ** Z[i]) * sz[A[i]] * (N-sz[A[i]]);
//   }
// 
//   wt(res);
// }