自己看

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

struct Road {
double s, k, w;
};

int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);

int n;
double EU;
cin >> n >> EU;

vector<Road> a(n);
for (auto &x : a) {
    cin >> x.s >> x.k >> x.w;
}

// 求 k * v^2 * (v - w) = c 的解
auto getSpeed = [&](double c, double k, double w) {
    double l = max(0.0, w);
    double r = max(1.0, l + 1.0);

    while (k * r * r * (r - w) < c) r *= 2.0;

    for (int it = 0; it < 60; ++it) {
        double mid = (l + r) * 0.5;
        if (k * mid * mid * (mid - w) < c)
            l = mid;
        else
            r = mid;
    }
    return (l + r) * 0.5;
};

auto totalEnergy = [&](double c) {
    double sum = 0.0;
    for (const auto &x : a) {
        double v = getSpeed(c, x.k, x.w);
        double d = v - x.w;
        sum += x.k * x.s * d * d;
    }
    return sum;
};

// EU = 0 时，根据题目保证可行，所有路段均可借顺风前进
if (EU == 0.0) {
    double ans = 0.0;
    for (const auto &x : a) ans += x.s / x.w;
    cout << fixed << setprecision(12) << ans << '\n';
    return 0;
}

double l = 0.0, r = 1.0;
while (totalEnergy(r) < EU) r *= 2.0;

for (int it = 0; it < 70; ++it) {
    double mid = (l + r) * 0.5;
    if (totalEnergy(mid) < EU)
        l = mid;
    else
        r = mid;
}

double c = (l + r) * 0.5;
double ans = 0.0;

for (const auto &x : a) {
    double v = getSpeed(c, x.k, x.w);
    ans += x.s / v;
}

cout << fixed << setprecision(8) << ans << '\n';
return 0;
}