## PIB '20 P2 - 2 + 2 = 5

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Points: 5 (partial)
Time limit: 0.5s
Memory limit: 128M

Author:
Problem type

Josh loves solving problems. However, solving problems takes a lot of time, so he will sometimes batch problems together, which allows him to solve them quicker. He will do it according to the following rules:

• Every 2 problems takes him 1 minute to solve (rounded down).
• Every 7 problems takes him 1 less minute to solve than usual.

Some examples:

• Solving problems takes Josh minutes. It takes him minutes to solve the problems usually. However, since he's solved problems, and every problems takes less minute, he will only take minutes.
• Solving problems takes Josh = minutes in total.
• Solving problem takes Josh minutes.

Josh has only minutes to solve as many problems as possible. Can you determine the maxmium number of problems he can solve?

#### Input Specification

The first line will contain the integer  .

#### Output Specification

Output the maximum number of problems Josh can solve in minutes. No further constraints.

#### Sample Input For Subtask 1

5

#### Sample Output For Subtask 1

15

#### Explanation For Sample For Subtask 1

Solving problems takes him minutes, which is exactly the amount of time he has.

#### Sample Input For Subtask 2

1000000007

#### Sample Output For Subtask 2

2800000021