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#include<bits/stdc++.h>
using namespace std;
typedef pair<double,int>p;
int n,m,s,ne[5000001],h[5000001],to[10000001],idx;
bool vis[10000001];
double dis[10000001],w[5000001];
void add(int u,int v,double c){
	to[++idx]=v;
	w[idx]=1-c;
	ne[idx]=h[u];
	h[u]=idx;
}void dj(){
	dis[s]=1;
	priority_queue<p,vector<p>,greater<p> >heap;
	heap.push({1.0,s});
	while(heap.size()){
		int t=heap.top().second;
		heap.pop();
		if(vis[t])continue;
		vis[t]=1;
		for(int i=h[t];i!=-1;i=ne[i]){
			int j=to[i];
			if(dis[j]<dis[t]*w[i]){
				dis[j]=dis[t]*w[i];
				heap.push({dis[j],j});
			}
		}
	}
}int main(){
	memset(h,-1,sizeof h);
	cin>>n>>m;
	while(m--){
		int a,b,c;
		cin>>a>>b>>c;
		add(a,b,double(c)/100.0);
		add(b,a,double(c)/100.0);
	}cin>>s;
	dj();
	cin>>s;
	cout<<fixed<<setprecision(8)<<100.0/dis[s]<<'\n';
	return 0;
}

求指正