#include<bits/stdc++.h>
#define LL long long
#define LLL __int128
#define uint unsigned
#define ldb long double
#define uLL unsigned long long
using namespace std;
const int N=2e3+5;
const LL INF=4e18;
int n,m;LL T,ans=INF,d[N][N];
vector<pair<int,LL>>G[N];
signed main(){
	cin.tie(0)->sync_with_stdio(0);
	cin>>n>>m>>T;
	if(n==1)return cout<<"0\n",0;
	for(int i=1;i<=m;++i){
		int u,v,l,c;cin>>u>>v>>l>>c;
		G[u].emplace_back(v,1ll*l*c);
		G[v].emplace_back(u,1ll*l*c);
	}
	memset(d,0x3f,sizeof(d));
	d[0][1]=0;
	for(int k=0;k<n;++k){
		for(int u=1;u<=n;++u)if(d[k][u]<INF)
			for(auto [v,w]:G[u])
				d[k+1][v]=min(d[k+1][v],d[k][u]+w);
	}
	for(int k=1;k<=n;++k)
		if(d[k][n]<=INF/k)ans=min(ans,d[k][n]*k);
	cout<<fixed<<setprecision(10)<<1.L*ans/T<<'\n';
	return 0;
}
/*
3 3 100
1 3 100 100
1 2 100 24
2 3 100 24
*/