[문제 요약] 자신이 일하고 있는 마트에서 한 물건의 가격이 Y그램당 X원입니다. 같은 물건을 팔고 있는 다른 모든 매장의 가격을 조사해서 Y그림당 X원의 형식으로 정리했습니다.

• 자신이 일하고 있는 마트에서 판매되고 있는 가격 (X Y)
• 다른 마트의 갯수 (N)
• 각 마트에서 판매되고 있는 가격 (X Y)

Matej and Filip decided to accept that challenge. They will visit N different supermarket chains in order to find mortadella not only cheaper than the one in NSC, but the cheapest on the market. If they are successful, they will be able to buy the cheapest mortadella in an NSC branch close to their school.

NSC was hoping that no one would be able to find cheaper mortadella since all supermarket chains (including NSC) express mortadella prices in a convoluted way: X dollars for Y grams of mortadella.

Write a program to, given mortadella prices in NSC as well as the remaining N chains, determine the price that Matej and Filip will have to pay for 1000 grams of mortadella in the NSC close to their school.

입력

• The first line of input contains two positive integers XNSC (1 ≤ XNSC ≤ 100) and YNSC (1 ≤ YNSC ≤ 1000), where XNSC is the price of YNSC grams of mortadella in the NSC chain.
• The second line of input contains the positive integer N (1 ≤ N ≤ 100), the number of supermarket chains (excluding NSC).
• Each of the following N lines contains two positive integers Xi (1 ≤ Xi ≤ 100) and Yi (1 ≤ Yi ≤ 1000), i=1..N, where Xi is the price of Yi grams of mortadella in the ith supermarket chain.

출력

입출력 예

input

5 100 
3 
4 100 3 100 7 100

output

30.00

input

13 6 
5 
56 679 35 120 99 999 56 73 37 532

output

69.55

input

100 5 
3 
99 8 65 14 78 10

output

4642.86

출처:coci/2012-2013/contest2 1/6
요약:ladown21