#include <bits/stdc++.h>

#define ld long double
#define ll long long
#define ull unsigned ll

#define f first
#define s second
#define pii pair < int, int >

#define pb push_back
#define mp make_pair

using namespace std;

const int MXN = 1e5 + 7;
const int MAXN = 1e2 + 1;
const ll INF = 1e16 + 1;
const int MOD = 1e9 + 7;
const double EPS = 1e-9;

ll n, m;
ll s, f;
ll x[MXN], y[MXN], val[MXN];
ll dp[MXN];
ll dp1[MXN];
vector < pii > g[MXN];
vector < pii > g1[MXN];
set < pair<long long, long long> > q;
set < pair<long long, long long> > q1;
int A, B;

void Dijkstra(int s, int f)
{
    int v;
    for(int i = 1; i <= n; i++)
    {
        dp[i] = INF;
    }
    dp[s] = 0;
    q.insert(mp(dp[s], s));
    while(!q.empty())
    {
        v = q.begin() -> second;
        q.erase(q.begin());
        for(int i = 0; i < g[v].size(); i++)
        {
            int to = g[v][i].f, len = g[v][i].s;
            if(dp[v] + len < dp[to])
            {
                q.erase(mp(dp[to], to));
                dp[to] = dp[v] + len;
                q.insert(mp(dp[to], to));
            }
        }
    }
    return;
}

long long Dijkstra1(int s, int f)
{
    int v;
    for(int i = 1; i <= n; i++)
    {
        dp1[i] = INF;
    }
    dp1[s] = 0;
    q1.insert(mp(dp1[s], s));
    while(!q1.empty())
    {
        v = q1.begin() -> second;
        q1.erase(q1.begin());
        for(int i = 0; i < g1[v].size(); i++)
        {
            int to = g1[v][i].f, len = g1[v][i].s;
            if(dp1[v] + len < dp1[to])
            {
                q1.erase(mp(dp1[to], to));
                dp1[to] = dp1[v] + len;
                q1.insert(mp(dp1[to], to));
            }
        }
    }
    return dp1[f] == INF ? -1 : dp1[f];
}


int main()
{
    cin >> n >> m >> s >> f;
    for(int i = 1; i <= m; i++)
    {
        cin >> x[i] >> y[i] >> val[i];
    }
    cin >> A >> B;
    for (int i =1; i  <= n; i++) {
        if (val[i] >= B) {
            g1[x[i]].pb(mp(y[i], val[i]));
            g1[y[i]].pb(mp(x[i], val[i]));
        } if (val[i] <= A) {
            g[x[i]].pb(mp(y[i], val[i]));
            g[y[i]].pb(mp(x[i], val[i]));
        }
    }
    Dijkstra(s, f);
    for (int i = 1; i <= n; i++) {
        if (dp[i] == INF) {
            g[s].pb(mp(i, dp[i]));
            g[i].pb(mp(s, dp[i]));
        }
    }
    cout << Dijkstra1(s, f);
    return 0;
}