IndiaHacks 2016 - Online Edition (Div. 1 + Div. 2)
D
Delivery Bears
Codeforces
2200
原题
← CE →
翻译中…

Niwel is a little golden bear. As everyone knows, bears live in forests, but Niwel got tired of seeing all the trees so he decided to move to the city.

翻译中…

In the city, Niwel took on a job managing bears to deliver goods. The city that he lives in can be represented as a directed graph with $*n*$ nodes and $*m*$ edges. Each edge has a weight capacity. A delivery consists of a bear carrying weights with their bear hands on a simple path from node $1$ to node $*n*$. The total weight that travels across a particular edge must not exceed the weight capacity of that edge.

翻译中…

Niwel has exactly $*x*$ bears. In the interest of fairness, no bear can rest, and the weight that each bear carries must be exactly the same. However, each bear may take different paths if they like.

翻译中…

Niwel would like to determine, what is the maximum amount of weight he can deliver (it's the sum of weights carried by bears). Find the maximum weight.

翻译中…

Input

翻译中…

The first line contains three integers $*n*$, $*m*$ and $*x*$ ($2 ≤ *n* ≤ 50$, $1 ≤ *m* ≤ 500$, $1 ≤ *x* ≤ 100 000$) — the number of nodes, the number of directed edges and the number of bears, respectively.

翻译中…

Each of the following $*m*$ lines contains three integers $*a*_{*i*}$, $*b*_{*i*}$ and $*c*_{*i*}$ ($1 ≤ *a*_{*i*}, *b*_{*i*} ≤ *n*$, $*a*_{*i*} ≠ *b*_{*i*}$, $1 ≤ *c*_{*i*} ≤ 1 000 000$). This represents a directed edge from node $*a*_{*i*}$ to $*b*_{*i*}$ with weight capacity $*c*_{*i*}$. There are no self loops and no multiple edges from one city to the other city. More formally, for each $*i*$ and $*j*$ that $*i* ≠ *j*$ it's guaranteed that $*a*_{*i*} ≠ *a*_{*j*}$ or $*b*_{*i*} ≠ *b*_{*j*}$. It is also guaranteed that there is at least one path from node 1 to node $*n*$.

翻译中…

Output

翻译中…

Print one real value on a single line — the maximum amount of weight Niwel can deliver if he uses exactly $*x*$ bears. Your answer will be considered correct if its absolute or relative error does not exceed $10^{ - 6}$.

翻译中…

Namely: let's assume that your answer is $*a*$, and the answer of the jury is $*b*$. The checker program will consider your answer correct if image.

翻译中…

Note

翻译中…

In the first sample, Niwel has three bears. Two bears can choose the path image, while one bear can choose the path image. Even though the bear that goes on the path image can carry one unit of weight, in the interest of fairness, he is restricted to carry 0.5 units of weight. Thus, the total weight is 1.5 units overall. Note that even though Niwel can deliver more weight with just 2 bears, he must use exactly 3 bears on this day.

翻译中…

样例

Input #1
4 4 3
1 2 2
2 4 1
1 3 1
3 4 2
Output #1
1.5000000000
InputCopy OutputCopy
Input #2
5 11 23
1 2 3
2 3 4
3 4 5
4 5 6
1 3 4
2 4 5
3 5 6
1 4 2
2 5 3
1 5 2
3 2 30
Output #2
10.2222222222
InputCopy OutputCopy
题目信息
题号
653D
时间限制
2 s
内存限制
256 MB
标签
二分
网络流
图论

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。