#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
const int N=2505;
const int M=2e4+5;
const int inf=1e18;

static char buf[1000000],*p1=buf,*p2=buf;
#define getchar() p1==p2&&(p2=(p1=buf)+fread(buf,1,1000000,stdin),p1==p2)?EOF:*p1++
inline int wrd(){int x=0,f=1;char c=getchar();while(c<'0' || c>'9'){if(c=='-') f=-1;c=getchar();}while(c>='0' && c<='9') {x=(x<<3)+(x<<1)+c-48;c=getchar();}return x*f;}
inline void write(int x){static char buf[20];static int len=-1;if(x<0)putchar('-'),x=-x;do buf[++len]=x%10,x/=10;while(x);while(len>=0)putchar(buf[len--]+48);}

int n,m,s,t,cnt,head[N];
struct edge{
	int to,w,nxt;
}e[M];
void add(int u,int v,int w){e[++cnt]={v,w,head[u]},head[u]=cnt;}

int f[N];
bool vs[N];

void dij(){
	priority_queue<pii> q;
	for(int i=1;i<=n;++i) f[i]=inf,vs[i]=0;
	f[s]=0,q.push({0,s});
	while(q.size()){
		int u=q.top().se; q.pop();
		if(vs[u]) continue;
		vs[u]=1;
		for(int i=head[u];i;i=e[i].nxt){
			int v=e[i].to;
			if(f[v]>f[u]+e[i].w){
				f[v]=f[u]+e[i].w;
				if(!vs[v]) q.push({-f[v],v});
			}
		}
	}
}

signed main(){
	n=wrd(),m=wrd(),s=wrd(),t=wrd();
	for(int i=1;i<=m;++i){
		int u=wrd(),v=wrd(),w=wrd();
		add(u,v,w),add(v,u,w);
	}
	dij(),write(f[t]);
}