Earthquake[USACO01OPEN]

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

template<typename T>
inline void read(T &num) {
	T x = 0, f = 1; char ch = getchar();
	for (; ch > '9' || ch < '0'; ch = getchar()) if (ch == '-') f = -1;
	for (; ch <= '9' && ch >= '0'; ch = getchar()) x = (x << 3) + (x << 1) + (ch ^ '0');
	num = x * f;
}

int n, m, F;

struct edge{
	int u, v, c, t;
	double val;
	bool operator < (const edge b) const {
		return val < b.val;
	}
} e[10005];

int fa[405];
int find(int x) {
	return fa[x] == x ? x : fa[x] = find(fa[x]);
}
bool check(double k) {
	for (int i = 1; i <= n; i++) fa[i] = i;
	for (int i = 1; i <= m; i++) {
		e[i].val = e[i].c * 1.0 + k * e[i].t;
	}
	sort(e + 1, e + m + 1);
	double ret = 0;
	for (int i = 1; i <= m; i++) {
		int tx = find(e[i].u), ty = find(e[i].v);
		if (tx != ty) {
			ret += e[i].val;
			fa[ty] = tx;
		}
	}
	return ret < F;
}

int main() {
	read(n); read(m); read(F);
	for (int i = 1; i <= m; i++) {
		read(e[i].u); read(e[i].v); read(e[i].c); read(e[i].t);
	}
	double l = 0, r = 2e9, mid = 0;
	while (r - l > 1e-7) {
		mid = (l + r) / 2;
		if (check(mid)) {
			l = mid + 0.000001;
		} else r = mid - 0.000001;
	}
	printf("%.4lf\n", l);
	return 0;
}