Problem:
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Problem Statement

We have planted $N$ flower seeds, all of which come into different flowers.
We want to make all the flowers come out together.

Each plant has a value called vitality, which is initially zero.
Watering and spreading fertilizers cause changes on it, and the $i$-th plant will come into flower if its vitality is equal to or greater than $\mathit{th}_i$.
Note that $\mathit{th}_i$ may be negative because some flowers require no additional nutrition.

Watering effects on all the plants.
Watering the plants with $W$ liters of water changes the vitality of the $i$-th plant by $W \times \mathit{vw}_i$ for all $i$ ($1 \le i \le n$), and costs $W \times \mathit{pw}$ yen, where $W$ need not be an integer.
$\mathit{vw}_i$ may be negative because some flowers hate water.

We have $N$ kinds of fertilizers, and the $i$-th fertilizer effects only on the $i$-th plant.
Spreading $F_i$ kilograms of the $i$-th fertilizer changes the vitality of the $i$-th plant by $F_i \times \mathit{vf}_i$, and costs $F_i \times \mathit{pf}_i$ yen, where $F_i$ need not be an integer as well.
Each fertilizer is specially made for the corresponding plant, therefore $\mathit{vf}_i$ is guaranteed to be positive.

Of course, we also want to minimize the cost.
Formally, our purpose is described as "to minimize $W \times \mathit{pw} + \sum_{i=1}^{N}(F_i \times \mathit{pf}_i)$ under $W \times \mathit{vw}_i + F_i \times \mathit{vf}_i \ge \mathit{th}_i$, $W \ge 0$, and $F_i \ge 0$ for all $i$ ($1 \le i \le N$)".
Your task is to calculate the minimum cost.

Input

The input consists of multiple datasets.
The number of datasets does not exceed $100$, and the data size of the input does not exceed $20\mathrm{MB}$.
Each dataset is formatted as follows.

$N$
$\mathit{pw}$
$\mathit{vw}_1$ $\mathit{pf}_1$ $\mathit{vf}_1$ $\mathit{th}_1$
:
:
$\mathit{vw}_N$ $\mathit{pf}_N$ $\mathit{vf}_N$ $\mathit{th}_N$

The first line of a dataset contains a single integer $N$, number of flower seeds.
The second line of a dataset contains a single integer $\mathit{pw}$, cost of watering one liter.
Each of the following $N$ lines describes a flower. The $i$-th line contains four integers, $\mathit{vw}_i$, $\mathit{pf}_i$, $\mathit{vf}_i$, and $\mathit{th}_i$, separated by a space.

You can assume that $1 \le N \le 10^5$, $1 \le \mathit{pw} \le 100$, $-100 \le \mathit{vw}_i \le 100$, $1 \le \mathit{pf}_i \le 100$, $1 \le \mathit{vf}_i \le 100$, and $-100 \le \mathit{th}_i \le 100$.

The end of the input is indicated by a line containing a zero.

Output

For each dataset, output a line containing the minimum cost to make all the flowers come out.
The output must have an absolute or relative error at most $10^{-4}$.

Sample Input

3
10
4 3 4 10
5 4 5 20
6 5 6 30
3
7
-4 3 4 -10
5 4 5 20
6 5 6 30
3
1
-4 3 4 -10
-5 4 5 -20
6 5 6 30
3
10
-4 3 4 -10
-5 4 5 -20
-6 5 6 -30
0

Output for the Sample Input

43.5
36
13.5
0

Solution in C (judge verdict: Wrong Answer)

// AOJ 2592: Flowers
// 2017.11.30 bal4u@uu

#include <stdio.h>

int vw[100002], pf[100002], vf[100002], th[100002];
int n, pw;

double calc(double x)
{
	int i;
	double t, ans = pw * x;
	
	for (i = 0; i < n; i++) {
		t = th[i] - x * vw[i];
		if (t > 0) ans += t / (double)vf[i] * pf[i];
	}
	return ans;
}

int main()
{
	int i;
	double l, r, lm, rm, x, y, t, ans;

	while (scanf("%d", &n) && n > 0) {
		scanf("%d", &pw);
		for (i = 0; i < n; i++) scanf("%d%d%d%d", vw+i, pf+i, vf+i, th+i);

		l = 0, r = 1000;
		ans = 1e10;
		for (i = 0; i < 50; i++) {
			lm = (l * 2 + r) / 3;
			rm = (l + r * 2) / 3;
			x = calc(lm);
			y = calc(rm);
			if (x < y) r = rm;
			else       l = lm;
			t = x; if (y < t) t = y;
			if (ans > t) ans = t;
		}
		printf("%.8lf\n", ans);
	}
	return 0;
}