FatMouse' Trade

Time Limit: 2 Seconds
Memory Limit: 65536 KB

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.

**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.

**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.

Sample Input

5 3

7 2

4 3

5 2

20 3

25 18

24 15

15 10

-1 -1

**Sample Output**

13.333

31.500

*
*

Author:

**CHEN, Yue**
Source:

**Zhejiang Provincial Programming Contest 2004**
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