To Fill or Not to Fill (25)

输入描述:

Each input file contains one test case.  For each case, the first line contains 4 positive numbers: Cmax (<= 100), the maximum capacity of the tank; D (<=30000), the distance between Hangzhou and the destination city; Davg (<=20), the average distance per unit gas that the car can run; and N (<= 500), the total number of gas stations.  Then N lines follow, each contains a pair of non-negative numbers: Pi, the unit gas price, and Di (<=D), the distance between this station and Hangzhou, for i=1,...N.  All the numbers in a line are separated by a space.

输出描述:

For each test case, print the cheapest price in a line, accurate up to 2 decimal places.  It is assumed that the tank is empty at the beginning.  If it is impossible to reach the destination, print "The maximum travel distance = X" where X is the maximum possible distance the car can run, accurate up to 2 decimal places.

50 1300 12 8<br/>6.00 1250<br/>7.00 600<br/>7.00 150<br/>7.10 0<br/>7.20 200<br/>7.50 400<br/>7.30 1000<br/>6.85 300

749.17