#include <iostream>
#include <vector>
#include <set>

using namespace std;

const int N = 100500;

struct Edge {
    int u;
    double ln, v;
};

int n, m;
double t;
vector<Edge> g[N];

double dijkstra(double x) {
    vector<double> d(n, -1.0);
    d[0] = 0;

    set<pair<double, int>> q;
    q.emplace(0.0, 0);

    while (!q.empty()) {
        auto [dv, v] = *q.begin();
        q.erase(q.begin());

        for (const Edge& e : g[v]) {
            int u = e.u;
            double du = dv + (e.ln / (e.v + x));
            if (d[u] < 0 || d[u] > du) {
                q.erase(pair<double, int>(d[u], u));
                d[u] = du;
                q.emplace(du, u);
            }
        }
    }
    return d[n - 1];
}

int main() {
    ios_base::sync_with_stdio(false);
    cin >> n >> m >> t; 

    for (int i = 0; i < m; ++i) {
        int v, u;
        double ln, s;
        cin >> v >> u >> ln >> s;
        v--; u--;
        Edge eu = {u, ln, s};
        g[v].push_back(eu);
        Edge ev = {v, ln, s};
        g[u].push_back(ev);
    }

    double lf = 0, rg = 1e18;
    for (int i = 0; i < 100; ++i) {
        double mid = (lf + rg) / 2;
        if (dijkstra(mid) <= t) {
            rg = mid;
        } else {
            lf = mid;
        }
    }

    cout.precision(10);
    cout << fixed << rg << endl;
    return 0;
}