import java.util.ArrayList;
import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Scanner;

class Edge {
	public Edge(int to, double dist, double speed) {
		this.to = to;
		this.dist = dist;
		this.speed = speed;
	}

	int to;
	double dist;
	double speed;

	public double distance(double extraV) {
		return dist / (speed + extraV);
	}
}

class PQEdge {
	int to;
	double dist;

	public PQEdge(int to, double dist) {
		this.to = to;
		this.dist = dist;
	}
}

class Vertex {
	ArrayList<Edge> edges;

	public Vertex() {
		this.edges = new ArrayList<>();
	}

	public void addEdge(int to, int l, int v) {
		edges.add(new Edge(to, l, v));
	}

	@Override
	public String toString() {
		return edges.toString();
	}
}

public class NickyEnMark {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		int n = scanner.nextInt();
		int m = scanner.nextInt();
		int t = scanner.nextInt();

		ArrayList<Vertex> graph = new ArrayList<>();
		graph.add(new Vertex());
		for (int i = 0; i < n; i++) {
			graph.add(new Vertex());
		}

		for (int i = 0; i < m; i++) {
			int a = scanner.nextInt();
			int b = scanner.nextInt();
			int l = scanner.nextInt();
			int v = scanner.nextInt();
			graph.get(a).addEdge(b, l, v);
			graph.get(b).addEdge(a, l, v);
		}

		double dist = distance(graph, n, 0);

		if (dist <= t) {
			System.out.println(0);
			return;
		}

		double lower = 0;
		double upper = 10e13;
		double mid = 0;
		for (int i = 0; i < 70; i++) {
			mid = (lower + upper) / 2;
			dist = distance(graph, n, mid);
//			System.out.println(dist + " - " + mid);
			if (dist > t) {
				lower = mid;
			} else {
				upper = mid;
			}
		}

		System.out.println(mid);
	}

	private static double distance(ArrayList<Vertex> graph, int n, double extraV) {
		double[] distances = new double[n + 1];
		boolean[] done = new boolean[n + 1];
		for (int i = 0; i < graph.size(); i++) {
			distances[i] = Double.MAX_VALUE;
		}

		distances[1] = 0;

		PriorityQueue<PQEdge> q = new PriorityQueue<>(Comparator.comparing(e -> e.dist));
		q.add(new PQEdge(1, 0));
		while (!q.isEmpty()) {
			PQEdge e = q.poll();
			if (e.to == n) {
				return distances[n];
			}
			if (done[e.to]) {
				continue;
			}
			done[e.to] = true;

			for (Edge ee : graph.get(e.to).edges) {
				double newDist = distances[e.to] + ee.distance(extraV);
				if (newDist < distances[ee.to]) {
					distances[ee.to] = newDist;
					q.add(new PQEdge(ee.to, newDist));
				}
			}
		}

		return distances[n];
	}
}