#include<bits/stdc++.h>
using namespace std;

using db=double;
const int N=200+10,M=2e3+10,INF=1e9;
inline int chkmin(int &x,int y){ return y<x?x=y,1:0; }
#define gc getchar()
#define rd read()
inline int read(){
	int x=0,f=0; char c=gc;
	for(;c<'0'||c>'9';c=gc) f|=(c=='-');
	for(;c>='0'&&c<='9';c=gc) x=(x<<1)+(x<<3)+(c^48);
	return f?-x:x;
}

int n,m,s,t,P,maxflow=0,mincost=0; db ans=INF;

int head[N],ne[M*2],v[M*2],fl[M*2],w[M*2],tot=1;
void add(int x,int y,int f,int z){
	ne[++tot]=head[x],head[x]=tot,v[tot]=y,fl[tot]=f,w[tot]=z;
	ne[++tot]=head[y],head[y]=tot,v[tot]=x,fl[tot]=0,w[tot]=-z;
}

int dis[N],vis[N],pre[N],idx[N]; queue<int> q;
int spfa(){
	for(int i=1;i<=n;++i) dis[i]=INF,vis[i]=0; q.push(s),dis[s]=0,vis[s]=1;
	while(!q.empty()){
		int u=q.front(); q.pop(),vis[u]=0;
		for(int i=head[u];i;i=ne[i])
			if(fl[i]&&chkmin(dis[v[i]],dis[u]+w[i]))
				pre[v[i]]=u,idx[v[i]]=i,q.push(v[i]),vis[v[i]]=1;
	}
	return dis[t]!=INF;
}

int main(){

	n=rd,m=rd,P=rd,s=rd,t=rd;
	for(int i=1,x,y,z,f;i<=m;++i) x=rd,y=rd,z=rd,f=rd,add(x,y,f,z);
	
	while(spfa()){
		int dflow=INF; for(int i=t;i!=s;i=pre[i]) dflow=min(dflow,fl[idx[i]]);
		maxflow+=dflow,mincost+=dis[t]*dflow;
		for(int i=t;i!=s;i=pre[i]) fl[idx[i]]-=dflow,fl[idx[i]^1]+=dflow;
		ans=min(ans,(db)(P+mincost)/maxflow);
	}
	
	printf("%.6lf\n", ans);

	return 0;
}