#include <bits/stdc++.h>

using namespace std;

const int INF = 1000000000;

int main() {

	int n, c, x, y, m, s, t, a, b;
	cin >> n >> m >> s >> t;
	s--;
	t--;
	vector < vector < pair<int,int> > > g (n);
	for (int i = 0; i < m; i++){
        cin >> x >> y >> c;
        g[x - 1].push_back(pair <int, int> (y - 1, c));
        g[y - 1].push_back(pair <int, int> (x - 1, c));
	}
    cin >> a >> b;
	vector<int> d (n, INF),  p (n);
	d[s] = 0;
	set < pair<int,int> > q;
	q.insert (make_pair (d[s], s));
	while (!q.empty()) {
		int v = q.begin()->second;
		q.erase (q.begin());

		for (size_t j=0; j<g[v].size(); ++j) {
			int to = g[v][j].first,
				len = g[v][j].second;
			if (d[v] + len < d[to] && d[v] + len <= a) {
				q.erase (make_pair (d[to], to));
				d[to] = d[v] + len;
				p[to] = v;
				q.insert (make_pair (d[to], to));
			}
		}
	}
	for (long long i = 0; i < n; i++)
        if (d[i] != INF)
            q.insert(pair <int, int> (d[i], i));
    //vector<int> d (n, INF),  p (n);
    while (!q.empty()) {
		int v = q.begin()->second;
		q.erase (q.begin());

		for (size_t j=0; j<g[v].size(); ++j) {
			int to = g[v][j].first,
				len = g[v][j].second;
			if (d[v] + len < d[to] && d[v] + len >= b) {
				q.erase (make_pair (d[to], to));
				d[to] = d[v] + len;
				p[to] = v;
				q.insert (make_pair (d[to], to));
			}
		}
	}
	if (d[t] != INF)
        cout << d[t];
    else
        cout << -1;
    cout << endl;
	return 0;
}


/*
4 6
1 4
1 2 4
2 4 4
4 1 6
1 3 7
4 3 10
3 2 2
5 6
*/