#include <bits/stdc++.h>
using namespace std;
const int N = 2000010;
long long n, m, s, l;
vector<pair<long long, long long> > Adj[N];
long long Dis[N], Ans;
set<pair<long long, long long> > Res;
vector<pair<long long, pair<long long, long long> > > Edges;
void Dik() {
  for (int i = 0; i <= n; i++) Dis[i] = 1e18;
  Dis[s] = 0;
  set<pair<long long, long long> > S;
  S.insert({0, s});
  while (!S.empty()) {
    auto Cur = *S.begin();
    S.erase(S.begin());
    for (int i = 0; i < Adj[Cur.second].size(); i++) {
      int to = Adj[Cur.second][i].first;
      long long w = Adj[Cur.second][i].second;
      if (Dis[to] > Cur.first + w) {
        Dis[to] = Cur.first + w;
        S.insert({Dis[to], to});
      }
    }
  }
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cin >> n >> m >> s;
  for (int i = 0; i < m; i++) {
    int a, b, w;
    cin >> a >> b >> w;
    Edges.push_back({w, {a, b}});
    Adj[a].push_back({b, w});
    Adj[b].push_back({a, w});
  }
  cin >> l;
  if (l == 0) {
    cout << 1 << endl;
    return 0;
  }
  Dik();
  for (int i = 1; i <= n; i++)
    if (Dis[i] == l) Ans++;
  for (int i = 0; i < Edges.size(); i++) {
    int a = Edges[i].second.first;
    int b = Edges[i].second.second;
    long long w = Edges[i].first;
    if (Dis[a] < l && Dis[a] + w > l && (w - (l - Dis[a])) + Dis[b] >= l) {
      Ans++;
    }
    if (Dis[b] < l && Dis[b] + w > l && (w - (l - Dis[b])) + Dis[a] >= l) {
      Ans++;
    }
    if (Dis[a] < l && Dis[a] + w > l && (w - (l - Dis[a])) + Dis[b] >= l) {
      if (Dis[b] < l && Dis[b] + w > l && (w - (l - Dis[b])) + Dis[a] >= l) {
        if (w - (l - Dis[a]) == (l - Dis[b])) Ans--;
      }
    }
  }
  cout << Ans << endl;
  return 0;
}
