PIB '20 P2 - 2 + 2 = 5

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

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Ada, Assembly, Awk, Brain****, C, C#, C++, COBOL, CommonLisp, D, Dart, F#, Forth, Fortran, Go, Groovy, Haskell, Intercal, Java, JS, Kotlin, Lisp, Lua, Nim, ObjC, OCaml, Octave, Pascal, Perl, PHP, Pike, Prolog, Python, Racket, Ruby, Rust, Scala, Scheme, Sed, Swift, TCL, Text, Turing, VB, Zig

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 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 takes 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 maxmium 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 further 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

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