#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <set>
using namespace std;

int n,m,s,len;
vector<pair<int,int> > g[100001];
int d[100001];

priority_queue<pair<int,int> > pq;

int main() {
	scanf("%d %d %d",&n,&m,&s);
	for (int i=0;i<m;i++) {
		int a,b,w;
		scanf("%d %d %d",&a,&b,&w);
		g[a].push_back(make_pair(b,w));
		g[b].push_back(make_pair(a,w));
	}
	scanf("%d",&len);
	memset(d,-1,sizeof(d));
	d[s]=0;
	pq.push(make_pair(0,s));
	while (!pq.empty()) {
		pair<int,int> p = pq.top();
		int id=p.second;
		int idd=-p.first;
		pq.pop();
		if (d[id]!=idd) continue;
		for (int i=0;i<(int)g[id].size();i++) {
			int id2=g[id][i].first;
			int w=g[id][i].second;
			if (d[id2]==-1 || d[id]+w<d[id2]) {
				d[id2]=d[id]+w;
				pq.push(make_pair(-d[id2],id2));
			}
		}
	}
	int st=0;
	for (int id=1;id<=n;id++) {
		if (d[id]==len) st++;
	}
	for (int id=1;id<=n;id++) {
		for (int i=0;i<(int)g[id].size();i++) {
			int id2=g[id][i].first;
			int w=g[id][i].second;
			if (id2<id) continue;
			int k1=len-d[id], k2=len-d[id2];
			if (0<k1 && k1<w && w-k1+d[id2]>=len) st++;
			if (0<k2 && k2<w && w-k2+d[id]>len) st++;
		}
	}
	printf("%d\n",st);
	return 0;
}