# FatMouse' Trade

Time Limit: 1 Second Memory Limit: 32768 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 31.500Submit

Source: Zhejiang Provincial Programming Contest 2004