#include <iostream>
#include <vector>
#include <queue>

using namespace std;

const long long INF = 1000000000000;

int main()
{
    int n, m, s, f, a, b;
    cin >> n >> m;
    vector< vector < pair <int, int> > > g(n + 5);
    cin >> s >> f;
    for (int i = 0; i < m; i++)
    {
        int x, y, d;
        cin >> x >> y >> d;
        g[x - 1].push_back(make_pair(y - 1, d));
        g[y - 1].push_back(make_pair(x - 1, d));
    }
    cin >> a >> b;
    queue<int> q;
    q.push(s - 1);
    vector<long long> d(n);
    for (int i = 0; i < n; i++)
        d[i] = INF;
    d[s - 1] = 0;
    while (!q.empty())
    {
        int v = q.front();
        q.pop();
        for (size_t i = 0; i < g[v].size(); ++i)
        {
            int to = g[v][i].first;
            if ((d[v] + g[v][i].second < d[to]) && g[v][i].second >= b)
            {
                q.push(to);
                d[to] = d[v] + g[v][i].second;
            }
        }
    }
    vector<long long> d1(n);
    for (int i = 0; i < n; i++)
        d1[i] = INF;
    d1[s - 1] = 0;
    q.push(s - 1);
    while (!q.empty())
    {
        int v = q.front();
        q.pop();
        for (size_t i = 0; i < g[v].size(); ++i)
        {
            int to = g[v][i].first;
            if ( (d1[v] + g[v][i].second < d1[to]) && g[v][i].second <= a)
            {
                q.push(to);
                d1[to] = d1[v] + g[v][i].second;
            }
        }
    }
    if (d[f - 1] == INF && d1[f - 1] == INF)
        cout << -1;
    else if (d[f - 1] < d1[f - 1])
        cout << d[f - 1];
    else
        cout << d1[f - 1];
    return 0;
}