#include<bits/stdc++.h>
using namespace std;
int e[2501][2501],n,m,s,t,a,b,c,f[2501],dis[2501],k,minn;
int main(){
	cin>>n>>m>>s>>t;
	memset(e,0x3f,sizeof(e));
	for(int i=1;i<=m;i++){
		scanf("%d%d%d",&a,&b,&c);
		e[a][b]=c;
		e[b][a]=c;
	}
	for(int i=1;i<=n;i++){
		dis[i]=0x3f;
		dis[i]=e[s][i];
	}
	dis[s]=0;
	f[s]=1;
	for(int i=1;i<=n-1;i++){
		minn=0x3f;
		for(int j=1;j<=n;j++){
			if(f[j]==0&&dis[j]<minn){
				minn=dis[j];
				k=j;
			}
		}
		f[k]=1;
		if(k==t){
			break;
		}
		for(int j=1;j<=n;j++){
			if(f[j]==0&&dis[k]+e[k][j]<dis[j]){
				dis[j]=dis[k]+e[k][j];
			}
		}
	}
	cout<<dis[t];
	return 0;
}