#include <bits/stdc++.h>
using namespace std;
const int MAXN = 400;
const int MAXM = 10000;
int n, m, f;
// 并查集
int fa[MAXN + 5];
int findFa(int x)
{
    if (x == fa[x])
        return x;
    return fa[x] = findFa(fa[x]);
}
// 存边
struct Edge
{
    int u, v, c, t;
    double w;
};
Edge e[MAXM + 5];
bool cmp(Edge a, Edge b)
{
    return a.w < b.w;
}
// 二分答案
bool check(double mid)
{
    // (f-sum{ci}) / sum{ti} >= mid
    // (f-sum{ci}) >= mid * sum{ti}
    // (f-sum{ci}) - sum{mid * ti} >= 0
    // f - sum{ci+mid*ti} >= 0
    // 先求 min(sum{ci+mid*ti})
    for (int i = 1; i <= m; i++)
        e[i].w = e[i].c + mid * e[i].t;
    sort(e + 1, e + m + 1, cmp);
    for (int i = 1; i <= n; i++)
        fa[i] = i;
    double sum = 0;
    for (int i = 1; i <= m; i++)
    {
        int u = e[i].u;
        int v = e[i].v;
        double w = e[i].w;
        int faU = findFa(u);
        int faV = findFa(v);
        if (faU == faV)
            continue;
        sum += e[i].w;
        fa[faU] = faV;
    }
    return f - sum >= 0;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n >> m >> f;
    for (int i = 1; i <= m; i++)
        cin >> e[i].u >> e[i].v >> e[i].c >> e[i].t;
    double l = 0;
    double r = f;
    while (r - l > 1e-6)
    {
        double mid = (l + r) / 2;
        if (check(mid))
            l = mid;
        else
            r = mid;
    }
    cout << fixed << setprecision(4) << l;
    return 0;
}