#include<iostream>
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;
int n,m,s,t,cnt,head[100001];
int dis[100001],vis[100001];
struct uio{
int to,nxt,wei;
}edge[10000001];
struct cmp{
bool operator () (int x,int y)
{return dis[x]>dis[y];};
};
priority_queue<int,vector<int>,cmp> que;
void add(int x,int y,int z)
{
edge[++cnt].nxt=head[x];
edge[cnt].to=y;
edge[cnt].wei=z;
head[x]=cnt;
}
void dijkstra()
{
memset(dis,0x3f,sizeof(dis));
dis[s]=0;
que.push(s);
while(!que.empty())
{
int x=que.top();
que.pop();
if(!vis[x])
{
vis[x]=1;
for(int i=head[x];i;i=edge[i].nxt)
{
int y=edge[i].to;
dis[y]=min(dis[y],dis[x]+edge[i].wei);
que.push(y);
}
}
}
}
int main()
{
scanf("%d%d%d%d",&n,&m,&s,&t);
for(int i=1;i<=m;i++)
{
int u,v,w;
scanf("%d%d%d",&u,&v,&w);
add(u,v,w);
}
dijkstra();
return 0;
}