#include <bits/stdc++.h>
using namespace std;
int n,m,i,j,k,ans,x,y,d;
vector<pair<int,int>>g[30005];
priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>>pq;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    freopen("file.in", "r", stdin);
    freopen("file.out", "w", stdout);
    cin>>n>>m>>x>>y;
    while (m--)
    {
        cin>>i>>j>>d;
        g[i].push_back({d,j});
        g[j].push_back({d,i});
    }
    vector<int>prev(n+1,-1);
    pq.push({0,x});
    while (!pq.empty())
    {
        int dist=pq.top().first;
        int u=pq.top().second;
        pq.pop();
        for (auto v : g[u])
        {
            if (prev[v.second]==-1)
            {
                pq.push({dist+v.first,v.second});
            }
        }
    }
}