#include<bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,j,k) for(int i=(j);i<=(k);i++)
#define per(i,j,k) for(int i=(j);i>=(k);i--)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
typedef vector<int> vi;
typedef pair<int,int> pi;

const int inf=1e18;
signed main(){
  	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
  	
  	int n,m,s,t; cin>>n>>m>>s>>t;
  	vector<vector<pi>> G(n+1);
  	rep(i,1,m){
  		int u,v,w; cin>>u>>v>>w;
  		G[u].pb(mp(v,w));
  		G[v].pb(mp(u,w));
  	}
  	vi dis(n+1, inf), vis(n+1);
  	dis[s]=0;
  	priority_queue<pi, vector<pi>, greater<pi>> Q;
  	Q.push(mp(0,s));
  	while(!Q.empty()){
  		int u=Q.top().se; Q.pop();
  		if(vis[u]){
  			continue;
  		}
  		vis[u]=1;
  		for(const pi &ed:G[u]){
  			int v=ed.fi, w=ed.se;
  			if(dis[v]>dis[u]+w){
  				dis[v]=dis[u]+w;
  				Q.push(mp(dis[v], v));
  			}
  		}
  	}
  	cout<< dis[t] <<'\n';
}