#include<iostream>
#include<queue>
#include<cstring>
using namespace std;
const int N=3000,M=7000;
int n,m,s,t,tot,d[N];
queue<int> q;
bool vis[N];
struct node{
	int ver,edge,next,head;
}f[N*4];
void add(int x,int y,int z){
	f[++tot].ver=y;
	f[tot].edge=z;
	f[tot].next=f[x].head;
	f[x].head=tot;
}
void spfa(){
	memset(d,0x3f,sizeof(d));
	memset(vis,0,sizeof(vis));
	d[1]=0;
	vis[1]=1;
	q.push(1);
	while(!q.empty()){
		int x=q.front();
		q.pop();
		vis[x]=0;
		for(int i=f[x].head;i;i=f[i].next){
			int y=f[i].ver,z=f[i].edge;
			if(d[y] > d[x]+z){
				d[y]=d[x]+z;
				//cout<<x<<" "<<y<<" "<<d[x]<<" "<<d[y]<<"\n";
				if(!vis[y]) q.push(y),vis[y]=1;
			}
		}
	}
}
int main(){
	cin>>n>>m>>s>>t;
	for(int i=1;i<=m;i++){
		int x,y,z;
		cin>>x>>y>>z;
		add(x,y,z);
		add(y,x,z);
	}
	spfa();
	cout<<d[t];
	return 0;
}