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

Some examples:

• Solving ~8~ problems takes Josh ~\frac 8 2 - \left\lfloor \frac 8 7 \right\rfloor = 4 - 1 = 3~ minutes. It takes him ~4~ minutes to solve the problems usually. However, since he's solved ~8~ problems, and every ~7~ problems take ~1~ less minute, he will only take ~4 - 1 = 3~ minutes.
• Solving ~7~ problems takes Josh ~\left\lfloor \frac 7 2 \right\rfloor - 1 = 2~ minutes in total.
• Solving ~1~ problem takes Josh ~0 - 0 = 0~ minutes.

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

Input Specification

The first line will contain the integer ~T~ ~(1 \le T \le 10^{14})~.

Output Specification

Output the maximum number of problems Josh can solve in ~T~ minutes.

Subtasks

Subtask 1 [37%]

~T \le 10^6~

Subtask 2 [63%]

No additional constraints.

Sample Input for Subtask 1

5

Sample Output for Subtask 1

15

Explanation for Sample for Subtask 1

Solving ~15~ problems takes him ~\left\lfloor \frac{15} 2 \right\rfloor - \left\lfloor \frac{15} 7 \right\rfloor = 7 - 2 = 5~ minutes, which is exactly the amount of time he has.

Sample Input for Subtask 2

1000000007

Sample Output for Subtask 2

2800000021