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

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> ii;
typedef vector<ll> vi;
typedef vector<vi> vvi;
typedef vector<ii> vii;

#define x first
#define y second
#define pb push_back
#define eb emplace_back
#define rep(i,a,b) for(auto i=(a); i<(b); ++i)
#define REP(i,n) rep(i,0,n)
#define all(v) (v).begin(), (v).end()
#define rs resize
#define DBG(x) cerr << __LINE__ << ": " << #x << " = " << (x) << endl

const ld PI = acos(-1.0);
template<class T> using min_queue =
priority_queue<T, vector<T>, greater<T>>;
template<class T> int sz(const T &x) {
    return (int) x.size(); // copy the ampersand(&)!
}

template<class T> ostream& operator<<(ostream &os, vector<T> &v) {
    os << "\n[";
    for(T &x : v) os << x << ',';
    return os << "]\n";
}

struct pairhash {
    public:
    template<typename T1, typename T2>
    size_t operator()(const pair<T1, T2> &p) const {
        size_t lhs = hash<T1>()(p.x);
        size_t rhs = hash<T2>()(p.y);
        return lhs ^ (rhs+0x9e3779b9+(lhs<<6)+(lhs>>2));
    }
};

struct road {
	ll v;
	ld d, l;
	road(ll _v, ld _d, ld _l) : v(_v), d(_d), l(_l) {}
};

void run() {
	ll n, m, t;
	cin >> n >> m >> t;
	vector<vector<road>> adj(n);
	for (ll i = 0; i < m; i++) {
		ll u, v, d, l;
		cin >> u >> v >> d >> l;
		u--; v--;
		road r1(v,d,l), r2(u,d,l);
		adj[u].pb(r1); adj[v].pb(r2);
	}
	ld lower = 0, upper = n*10'000'000;
	while (upper - lower > 0.00000001) {
		ld mid = (lower + upper)/2;
		vector<ld> d(n, n*10'000'000);
		d[0] = 0;
		set<pair<ld, ll>> Q{pair<ld,ll>{0,0}};
		while (!Q.empty()) {
			int v = Q.begin()->y;
			Q.erase(Q.begin());
			for (road r : adj[v]) if (d[v] + r.d/(r.l + mid) < d[r.v]) {
				Q.erase(ii(d[r.v], r.v));
				Q.emplace(d[r.v] = d[v] + r.d/(r.l + mid), r.v);
			}
		}
		if (d[n-1] <= t) {
			upper = mid;
		} else {
			lower = mid;
		}
	}
	cout << lower << endl;
}

signed main() {
    // DON'T MIX "scanf" and "cin"!
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout << fixed << setprecision(20);
    run();
    return 0;
}