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Topoland is home to a farmer named Vladimir, who sells milk, sourced from his healthy cows grazing in the lush meadows of the land. He recently introduced a special promotion: for giving away \(3\) of empty milk bottles, you get a \(1\) full bottle of milk free! How many bottles of milk are you able to consume using this promotion if you have already purchased \(n\) bottles of milk?

PS. Vladimir will be happy to lend you empty bottles, provided you return them later.

Source: https://onlinejudge.org/external/111/11150.pdf

Specification

Input

  • \(n\) - The number of purchased bottles of milk from the range \([1,200]\)

Output

  • The maximum number of bottles of milk that can be drunk using the promotion.

Example

Input

8

Output

12

Info

Explanation

At the beginning we have \(8\) full bottles of milk. If we borrow one empty bottle, we can exchange our \(9\) of empty bottles for \(3\) of new bottles. We drink \(3\) bottles of milk and exchange them for one bottle of milk. We drink it too, and at the end we give back the empty bottle. So we drank first \(8\), then \(3\) and finally \(1\) bottle of milk:

\(8+3+1=12\)