Choir essay P88452


Statement
 

pdf   zip

html

Mr. Whitacre is having a lot of fun assaying with his choir. However, it is a bit late and he will have to go home sooner or later. Furthermore, it is starting to snow and the streets are getting worse by the minute. How much time can Mr. Whitacre enjoy before departing?

Let us model the city as an undirected graph with n vertices (street crosses, numbered from 0) and m edges (streets). Mr. Whitacre is currently at vertex 0, and he has to reach vertex n−1 (home). The cost to traverse each street i is ai t + bi, where t denotes the time when Mr. Whitacre starts traversing that street. For instance, if he starts walking that street right now, the time to traverse it is just bi. Mr. Whitacre must be at home at most at time T.

Input

Input is all integer numbers, and consists of several cases, each with n, m and T, followed by the information of the m streets xi yi ai bi. Assume 2 ≤ n ≤ 104, 0 ≤ m ≤ 5n, 1 ≤ T ≤ 106, xiyi, that between two vertices there is no more than one edge, and that ai and bi are between 0 and 1000.

Output

For every case, print the maximum choir assay time with three digits after the decimal point. If it is impossible to reach home at time T, print “impossible”. The input cases have no precision issues.

Public test cases
  • Input

    2 1 10
    0 1 2 3
    
    3 1 1000
    1 2 0 0
    
    5 5 100
    4 0 10 0  0 3 2 10  2 4 1 5
    4 3 1 20  3 2 0 10
    

    Output

    2.333
    impossible
    10.000
    
  • Information
    Author
    Damià Torres
    Language
    English
    Official solutions
    C++
    User solutions
    C++
    Event
    Setzè Concurs de Programació de la UPC - Final
    Date
    2018-09-19