问题 21378 --Greedy Mouse## 21378: Greedy Mouse

时间限制: 1 Sec 内存限制: 64 MB

提交: 15 解决: 8

[提交][状态][讨论版][数据上传:][下载FPS1元][添加到购物车][下载测试数据1元][20kb]## 题目描述

A fat mouse prepared M pounds of cat food, ready to trade with the cats guarding the warehouse containing his favorite food:peanut. The warehouse has N rooms. The ith room containsW[i] pounds of peanut and requires F[i] pounds of cat food. Fatmouse does not have to trade for all the peanut in the room, instead, he may get W[i]*a% pounds of peanut if he pays F[i]*a% pounds of cat food. The mouse is a greedy mouse, so can you tell him the maximum amount of peanut he can obtain.

## 输入

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 W[i] and F[i] respectively. The
test case is terminated by two -1. All integers are not greater than
1000.

## 输出

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

## 样例输入

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

## 样例输出

13.333
31.500

## 提示

## 来源

[提交][状态]