\(6^{th}\) round, February \(6^{th}\) 2016
Young Mr. Potato is opening two new stores where he will, you guessed it, sell potatoes. Mr. Potato
gets his potatoes from \(N\) farmers. Each farmer offers exactly \(a@@RISE_MATH_BLOCK_0@@i\). Mr. Potato is going to buy all bags of potatoes from all farmers and place the bags in his two
stores.
Let’s denote the average potato price in the first store with \(P\)1, and the average potato price in the
second store with \(P_{2}\). The average potato price in a store is equal to the ratio of the price and the
total number of potatoes in the store. Taking into account logistical difficulties and the amount
of potatoes in the stores, he wants the product of the average prices of potatoes in the stores to be
minimal. In other words, he wants the product of \(P\)1 and \(P\)2 to be minimal.
After Mr. Potato settles on a division of bags in the stores, at least one store must have exactly \(L\)
bags.

In at least 30% of examples, it will hold \(N\) ⩽20.

The first line of input contains two integers \(N\) and \(L\) (2 ⩽\(N\) ⩽100, 1 ⩽\(L < N\)), the number of
potato bags and the number of potato bags in at least one store.
The second line of input contains \(N\) integers \(a@@RISE_MATH_BLOCK_0@@i\) ⩽100), separated by space.
The third line of input contains \(N\) integers \(c@@RISE_MATH_BLOCK_1@@i\) ⩽1 000 000), separated by space.
The sum of all \(a\)\(i\) will be ⩽500.

The first and only line of output must contain the minimal product of \(P\)1 and \(P\)2 from the task, rounded
to three decimal places.

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출처 COCI 2015/2016 Contest 6