# include <iostream>
# include <cmath>
# include <vector>
# include <algorithm>
# include <string>
# include <set>
# include <map>
# include <bitset>
# include <queue>
# include <iomanip>
# include <string>

# define FILE
# define x first
# define y second
using namespace std;

const int N = 1e5 + 100;

int n, m, s, t, A, B;
long long dist[N][2];
vector < pair < int, int > > gr[N];
set < pair < long long, pair < int, int > > > st;

int main()
{
    # ifdef FILE
        freopen( "travel.in", "r", stdin );
        freopen( "travel.out", "w", stdout );
    # endif // FILE

    # ifdef FILEs
        freopen( "input.txt", "r", stdin );
        freopen( "output.txt", "w", stdout );
    # endif // FILE
    ios_base::sync_with_stdio( false );

    cin >> n >> m;
    cin >> s >> t;
    for( int i = 1; i <= m; i ++ ){
        int a, b, c;
        cin >> a >> b >> c;
        gr[a].push_back( make_pair( c, b ) );
        gr[b].push_back( make_pair( c, a ) );
    }
    cin >> A >> B;
    for( int i = 1; i <= n; i ++ ){
        dist[i][0] = dist[i][1] = 1e18;
    }
    dist[s][0] = dist[s][1] = 0;
    st.insert( make_pair( 0, make_pair( s, 0 ) ) );
    st.insert( make_pair( 0, make_pair( s, 1 ) ) );

    while( st.empty() == false ){
        auto sp = *st.begin();
        st.erase( sp );
        long long d = sp.first;
        int v = sp.second.first;
        int tp = sp.second.second;
        for( auto to: gr[v] ){
            if( to.first >= B && dist[to.second][1] > d + to.first ){
                    st.erase( make_pair( dist[to.second][1], make_pair( to.second, 1 )) );
                    dist[to.second][1] = d+to.first;
                    st.insert( make_pair( dist[to.second][1], make_pair( to.second, 1 )) );
                }
            if( tp == 0 ){
                if( to.first <= A && dist[to.second][0] > d + to.first ){
                    st.erase( make_pair( dist[to.second][0], make_pair( to.second, 0 )) );
                    dist[to.second][0] = d+to.first;
                    st.insert( make_pair( dist[to.second][0], make_pair( to.second, 0 )) );
                }
            }
        }
    }
    long long mn = min( dist[t][0], dist[t][1] );
    if( mn == 1e18 ){
        cout << -1;
    }
    else{
        cout << mn;
    }
    # ifdef FILEs
        cout << endl << "------------------------";
        cout << endl << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s. |";
        cout << endl << "------------------------";
    # endif
    return 0;
}