#include<bits/stdc++.h>
using namespace std;
#define int long long
const int NR=5e3+10;
const int MR=1e5+10;
int n,m,s,t,P,ans1,ans2;
const int INF=1e18;

struct edge{
	int to,next,flow,cost;
}g[MR];
int tot=1,fte[NR];
void add(int x,int y,int z,int v){
	g[++tot]=(edge){y,fte[x],z,v};fte[x]=tot;
	g[++tot]=(edge){x,fte[y],0,-v};fte[y]=tot;
}

int h[NR],dis[NR],vis[NR],st[NR*NR],L,R;
bool SPFA(){
	memset(h,999999,sizeof(h));
	h[s]=0;st[L=R=1]=s;
	while(L<=R){
		int x=st[L];L++;vis[x]=0;
		for(int i=fte[x];i;i=g[i].next)
			if(g[i].flow&&h[g[i].to]>h[x]+g[i].cost){
				h[g[i].to]=h[x]+g[i].cost;
				if(!vis[g[i].to])st[++R]=g[i].to,vis[g[i].to]=1;
			}
	}
	return h[t]<INF;
}
struct point{
	int dis,id;
	bool operator <(const point &T)const{
		return dis>T.dis;
	}
};
priority_queue<point>q;
int nxt[NR],idx[NR];
bool dijkstra(){
	memset(dis,999999,sizeof(dis));
	memset(vis,0,sizeof(vis));
	dis[s]=0;q.push(point{0,s});
	while(!q.empty()){
		int x=q.top().id;q.pop();
		if(vis[x])continue;
		vis[x]=1;
		for(int i=fte[x];i;i=g[i].next)
			if(g[i].flow){
				int tmp=g[i].cost+h[x]-h[g[i].to];
				if(dis[g[i].to]>dis[x]+tmp){
					dis[g[i].to]=dis[x]+tmp;
					q.push(point{dis[g[i].to],g[i].to});
					idx[g[i].to]=i;nxt[g[i].to]=x;
				}
			}
	}
	return dis[t]<INF;
}
#define db double
db ans=1e18;
void Dinic(){
	SPFA();
	while(dijkstra()){
//	for(int i=1;i<=n;i++)printf("%lld ",nxt[i]);puts("");
		int minf=1e18;
		for(int i=t;i!=s;i=nxt[i])minf=min(minf,g[idx[i]].flow);
		ans1+=minf;ans2+=minf*(dis[t]+h[t]);
		ans=min(ans,1.0*(P+ans2)/ans1);
		for(int i=t;i!=s;i=nxt[i]){
			g[idx[i]].flow-=minf;
			g[idx[i]^1].flow+=minf;
		}
		for(int i=1;i<=n;i++)h[i]+=dis[i];
	}
}

signed main(){
	cin>>n>>m>>P>>s>>t;
	for(int i=1,x,y,z,w;i<=m;i++)
		scanf("%lld%lld%lld%lld",&x,&y,&z,&w),add(x,y,w,z);
	Dinic();
	printf("%.10lf\n",ans);
	return 0;
}