#include <iostream>
#include <queue>
#include <unordered_map>
#include <vector>
#include <climits>
#include <string>
using namespace std;
typedef long long int64;
const int64 MAX_COST = (LLONG_MAX >> 6);

struct Map1
{
    int id;
    int64 cost;
    bool operator<(const Map1& m) const {
        return cost > m.cost;
    }
};
struct Map2
{
    int64 cost = MAX_COST;
    unordered_map<int, bool> prev;
};
unordered_map<int, unordered_map<int, int64>> cost;
Map2 root[200];
int n, m, s, g;

int64 min_cost(int start, int end) {
    for(int i = 0; i < n; i++)
        root[i].cost = MAX_COST;
    priority_queue<Map1> q;
    root[start].cost = 0;
    for(auto c : cost[start]) {
        Map1 m = {c.first, c.second};
        root[c.first].prev[start] = true;
        root[c.first].cost = c.second;
        q.push(m);
    }
    while(!q.empty()) {
        int cur = q.top().id;
        q.pop();
        for(auto c : cost[cur]) {
            int64 d = root[cur].cost + c.second;
            if(d < root[c.first].cost) {
                Map1 m = {c.first, d};
                q.push(m);
                root[c.first].prev.clear();
                root[c.first].prev[cur] = true;
                root[c.first].cost = d;
            }
            else if(d == root[c.first].cost) {
                //Map1 m = {c.first, d};
                //q.push(m);
                root[c.first].prev[cur] = true;
            }
        }
    }
    return root[end].cost;
}

string enumerate(int i)
{
    int size = root[i].prev.size();
    if(size == 0)
        return to_string(i);
    string res = "a";
    char c = '0' + i;
    for(auto p : root[i].prev) {
        string str = enumerate(p.first) + c;
        if(str < res)
            res = str;
    }
    return res;
}

int main(void)
{
    cin >> n >> m >> s >> g;
    for(int i = 0; i < m; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        cost[b][a] = cost[a][b] = c;
    }
    min_cost(s, g);
    string res = enumerate(g);
    for(int i = 0; i < res.size(); i++)
        if(i == 0)
            cout << res[i];
        else
            cout << " " << res[i];
    cout << endl;
    return 0;
}