#include<iostream>
#include<climits>
#include<cmath>
using namespace std;
const int MAXN=20001;
const int MAXM=40001;
struct Edge{
	int u=0;
	int v=0;
	int w=0;
	int next=-1;
}edge[2*MAXM];
int dp[MAXN];
int head[MAXN];
int n,m,s,t;
void solve(int u,int k,int value){
	if(value<dp[u])dp[u]=value;
	else return;
	if(u==s)return;
	int pos=head[u];
	while(pos!=-1){
		solve(edge[pos].v,k+1,value+floor(edge[pos].w/k*1.0));
		pos=edge[pos].next;
	}
}
int main(){
	cin>>n>>m>>s>>t;
	int temp[n+1];
	for(int i=1;i<=n;i++){
		head[i]=-1;
		temp[i]=-1;
		dp[i]=INT_MAX;
	}
	for(int i=1;i<=2*m;i++){
		int u,v,w;
		cin>>u>>v>>w;
		edge[i].u=u;edge[i].v=v;edge[i].w=w;
		if(head[u]==-1)head[u]=i;
		if(temp[u]!=-1){
			edge[temp[u]].next=i;
		}
		temp[u]=i;
		i++;
		edge[i].u=v;edge[i].v=u;edge[i].w=w;
		if(head[v]==-1)head[v]=i;
		if(temp[v]!=-1){
			edge[temp[v]].next=i;
		}
		temp[v]=i;
	}
	solve(t,1,0);
	cout<<dp[s];
	return 0;
}