#include<queue>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define N 20000
#define maxn 9999999
using namespace std;
double dis[N],z;
int n,m,x,y,s,t,tot,head[N];
struct Edge
{
    int to,from,next;
    double dis;
}edge[N];
int read()
{
    ,f=; char ch=getchar();
    ; ch=getchar();}
    +ch-'; ch=getchar();}
    return x*f;
}
int add(int x,int y,double z)
{
    tot++;
    edge[tot].to=y;
    edge[tot].dis=z;
    edge[tot].next=head[x];
    head[x]=tot;
}
int spfa(int s)
{
    queue<int>q; bool vis[N];
    ;i<=n;i++) dis[i]=maxn,vis[i]=false;
    q.push(s),vis[s]=;
    while(!q.empty())
    {
        int x=q.front();q.pop();
        for(int i=head[x];i;i=edge[i].next)
        {
            int t=edge[i].to;
            if(dis[t]>dis[x]+edge[i].dis)
            {
                dis[t]=dis[x]+edge[i].dis;
                if(!vis[t])
                {
                    q.push(t);
                    vis[t]=true;
                }
            }
        }
        vis[x]=false;
    }
}
int main()
{
    n=read(),m=read();
    ;i<=m;i++)
    {
        x=read(),y=read();
        scanf("%lf",&z);
        z=(-z)/;
        add(x,y,z);add(y,x,z);
    }
    s=read(),t=read();
    spfa(s);
    /dis[t];
    printf("%.8lf",ans);
}