#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N = 200010;
const int M = 200010;
const int inf = 1e17;

struct node{
    int u, dist;
    bool operator <(const node a)const{
        return dist > a.dist;
    }
};

int n, m, s, L, cnt, dis[N], head[N], nxt[M], to[M], w[M], vis[N];

int U[N], V[N];

priority_queue <node> q;

inline int read()
{
    int x = 0, f = 1;
    char c = getchar();
    while(c < '0' || c > '9') { if(c == '-') f = -1; c = getchar(); }
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}

void addedge(int u, int v, int k)
{
    to[++cnt] = v, w[cnt] = k;
    nxt[cnt] = head[u], head[u] = cnt;
}

void dijkstra()
{
    for(int i = 0; i <= n; i++) dis[i] = inf;
    dis[s] = 0, q.push((node){s, 0});
    while(!q.empty()){
        node now = q.top(); q.pop();
        if(vis[now.u]) continue;
        vis[now.u] = 1;
        for(int i = head[now.u]; i; i = nxt[i]){
            int v = to[i];
            if(dis[v] > dis[now.u] + w[i])
                dis[v] = dis[now.u] + w[i], q.push((node){v, dis[v]});
        }
    }
}

signed main()
{
    n = read(), m = read(), s = read(), L = read();
    s = 0;
    for(int i = 1, u, v, k; i <= m; i++){
        u = read(), v = read(), k = read();
        U[i] = u, V[i] = v;
        addedge(u, v, k);
    }
    dijkstra();
    int ans = 0;
    for(int i = 1; i <= m; i++){
        if(2 * min(dis[U[i]], dis[V[i]]) < L) ans++;
    }
    printf("%d\n", ans);
    return 0;
}