#include <bits/stdc++.h>
#define ll long long
#define sz(x) (int)(x).size()
#define debug(v,n) for (int i = 1; i <= (n); ++i) cout << v[i] << " ";
#define next cout << '\n'
using namespace std;

const int N = 30005;
vector<pair<int,int>> graf[N];
int n, m, x, y;

struct cmp {
    bool operator()(int a, int b) {
        return sz(graf[a]) > sz(graf[b]);
    }
};
priority_queue<int, vector<int>, cmp> coada;

int main() {
    //ifstream fin("date.in.txt");
    ifstream fin("sate.in");
    ofstream fout("sate.out");
    fin >> n >> m >> x >> y;

    for (int i = 1; i <= m; ++i) {
        int a, b, d;
        fin >> a >> b >> d;
        graf[a].push_back({b, d});
        graf[b].push_back({a, d});
    }
    for (int i = x; i <= y; ++i)
            coada.push(i);

    while(!coada.empty()) {
        int nod = coada.top();
        coada.pop();
        /*

        */
        for (int i = 0; i < sz(graf[nod]); ++i) {
            int act = graf[nod][i].first, lgAct = graf[nod][i].second;
            for (int j = i + 1; j < sz(graf[nod]); ++j) {
                int to = graf[nod][j].first, lg = graf[nod][j].second;
                if(to > act) {
                    graf[act].push_back({to, lg + lgAct});
                    graf[to].push_back({act, lg + lgAct});
                }
                else {
                    graf[to].push_back({act, lg - lgAct});
                    graf[act].push_back({to, lg - lgAct});
                }
            }
        }
    }
    for (int i = 0; i < sz(graf[x]); ++i) {
        if(graf[x][i].first == y) {
            fout << graf[x][i].second;
            return 0;
        }
    }

    return 0;
}