#include <bits/stdc++.h>

using namespace std;

const int INF = 1000000000;
const int N = 2 * 100000;

#define make make_pair
#define x first
#define y second

vector < pair <int, int> > a[N];
priority_queue < pair <int, int> > q;
int d[N];

int main()
{
    int n, m, s, t, A, B;
    cin >> n >> m;

    cin >> s >> t;
    s--;
    t--;

    for (int i = 0; i < m; i++)
    {
        int x, y, z;
        cin >> x >> y >> z;
        x--;
        y--;

        a[x].push_back(make(y, z));
        a[y].push_back(make(x, z));
    }

    cin >> A >> B;

    for (int i = 0; i <= n; i++)
        d[i] = INF;
    d[s] = 0;

    q.push(make(0, s));

    while (!q.empty())
    {
        int v = q.top().y;
        int cur = -q.top().x;
        q.pop();

        if (cur > d[v])
            continue;

        for (int j = 0; j < (int)a[v].size(); j++)
        {
            int to = a[v][j].x;
            int len = a[v][j].y;

            if (d[v] + len < d[to] && len <= A)
            {
                d[to] = d[v] + len;
                q.push(make(-d[to], d[to]));
            }
        }
    }

    for (int i = 0; i < n; i++)
        if (d[i] != INF)
            q.push(make(d[i], i));

    while (!q.empty())
    {
        int v = q.top().y;
        int cur = -q.top().x;
        q.pop();

        if (cur > d[v])
            continue;

        for (int j = 0; j < (int)a[v].size(); j++)
        {
            int to = a[v][j].x;
            int len = a[v][j].y;

            if (d[v] + len < d[to] && len >= B)
            {
                d[to] = d[v] + len;
                q.push(make(-d[to], d[to]));
            }
        }
    }

    if (d[t] != INF)
        cout << d[t] << endl;
    else
        cout << -1 << endl;
    return 0;
}