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

#define int long long

const int N=2e5+1e3+7;

struct ND {
    int s;
    int d;
};

ND operator +(const ND &a,const ND &b)
{
    return {a.s+b.s,a.d+b.d};
}

bool operator <(const ND &a,const ND &b)
{
    if(a.d!=b.d)
        return a.d>b.d;
    return a.s<b.s;
}

int n,m;

vector<pair<int,ND> >g[N];

ND d[N];

int use[N];

priority_queue<pair<ND,int> > q;

int p;

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>m>>p;
    for(int i=1;i<=m;i++)
    {
        int u,v;
        int d,p;
        cin>>u>>v>>d>>p;
        g[u].push_back({v,{p,d}});
        g[v].push_back({u,{p,d}});
    }
    for(int i=1;i<=n;i++)
        d[i]={(int)0,(int)1e18};
    d[1]={0,0};
    q.push({d[1],1});
    while(!q.empty())
    {
        auto [w,x]=q.top();
        q.pop();
        if(use[x])
            continue;
        use[x]=1;
        for(auto [v,e]:g[x])
        {
            if(d[v]<d[x]+e)
            {
                d[v]=d[x]+e;
                q.push({d[v],v});
            }
        }
    }
    double ans=0;
    for(int x=1;x<=n;x++)
        for(auto [y,e]:g[x])
        {
            {
                int r=p-d[x].d*2;
                double s=d[x].s*2;
                if(r>=0)
                    ans=max(ans,1.0*r*e.s/e.d+s);
            }
            {
                int r=p-d[x].d-d[y].d-e.d;
                double s=d[x].s+d[y].s+e.s;
                if(r>=0)
                    ans=max(ans,1.0*r*e.s/e.d+s);
            }
        }
    cout<<fixed<<setprecision(15)<<ans<<"\n";
}