Time limit: 1 Seconds

Memory limit: 32768K

FatMouse prepared M pounds of cat food, ready to trade with the cats guarding the warehouse containing his favorite food, JavaBean.

The warehouse has N rooms. The i-th room contains J[i] pounds of JavaBeans and requires F[i] pounds of cat food. FatMouse does not have to trade for all the JavaBeans in the room, instead, he may get J[i]* a% pounds of JavaBeans if he pays F[i]* a% pounds of cat food. Here a is a real number. Now he is assigning this homework to you: tell him the maximum amount of JavaBeans he can obtain.

## 1. Input

The input consists of multiple test cases. Each test case begins with a line containing two non-negative integers M and N. Then N lines follow, each contains two non-negative integers J[i] and F[i] respectively. The last test case is followed by two -1's. All integers are not greater than 1000.

## 2. Output

For each test case, print in a single line a real number accurate up to 3 decimal places, which is the maximum amount of JavaBeans that FatMouse can obtain.

## 3. Sample Input

{{{5 3 7 2 4 3 5 2 20 3 25 18 24 15 15 10 -1 -1}}}

## 4. Sample Output

{{{13.333 31.500}}}

```   1 /*Written by czk*/
2 #include <iostream>
3 #include <iomanip>
4 #include <queue>
5 using namespace std;
6 struct room{
7         int java_bean;
8         int cat_food;
9         bool operator<(const room &r) const{
10                 return static_cast<double>(java_bean) / cat_food < static_cast<double>(r.java_bean) / r.cat_food;
11         }
12 };
13
14 int main() {
15         while(1) {
16                 int m, n;
17                 cin >> m >> n;
18                 if (m == -1 && n == -1) break;
19                 priority_queue<room> rooms;
20                 for(int i = 0; i < n; i++) {
21                         room r;
22                         cin >> r.java_bean >> r.cat_food;
23                         rooms.push(r);
24                 }
25                 double total = 0.0;
26                 while(!rooms.empty() && m > 0) {
27                         if(m>rooms.top().cat_food) {
28                                 total += rooms.top().java_bean;
29                                 m -= rooms.top().cat_food;
30                         } else {
31                                 total += static_cast<double>(rooms.top().java_bean) / rooms.top().cat_food * m;
32                                 m = 0;
33                         }
34                         rooms.pop();
35                 }
36                 cout << fixed<<setprecision(3) << total  << endl;
37         }
38
39 }
```

zju2109 (last edited 2008-02-23 15:35:02 by localhost)

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