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

using namespace std;

const double INF = 1e14;

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

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

double bellman_ford(double x) {
    vector<double> d(n, INF);
    d[0] = 0;

    for (int i = 0; i < n; ++i) {
        for (const auto& e : g) {
            double len = (e.ln / (e.s + x));
            if (d[e.u] < INF && d[e.v] >= d[e.u] + len) {
                d[e.v] = d[e.u] + len;
            }
            if (d[e.v] < INF && d[e.u] >= d[e.v] + len) {
                d[e.u] = d[e.v] + len;
            }
        }
        if (d[n - 1] <= t) {
            break;
        }
    }
        
    return d[n - 1];
}

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

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

    double lf = 0, rg = INF;
    for (int i = 0; i < 80; ++i) {
        double mid = (lf + rg) / 2;
        if (bellman_ford(mid) <= t) {
            rg = mid;
        } else {
            lf = mid;
        }
    }

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