100532: [AtCoder]ABC053 C - X: Yet Another Die Game

Problem Statement

Snuke has decided to play with a six-sided die. Each of its six sides shows an integer $1$ through $6$, and two numbers on opposite sides always add up to $7$.

Snuke will first put the die on the table with an arbitrary side facing upward, then repeatedly perform the following operation:

• Operation: Rotate the die $90°$ toward one of the following directions: left, right, front (the die will come closer) and back (the die will go farther). Then, obtain $y$ points where $y$ is the number written in the side facing upward.

For example, let us consider the situation where the side showing $1$ faces upward, the near side shows $5$ and the right side shows $4$, as illustrated in the figure. If the die is rotated toward the right as shown in the figure, the side showing $3$ will face upward. Besides, the side showing $4$ will face upward if the die is rotated toward the left, the side showing $2$ will face upward if the die is rotated toward the front, and the side showing $5$ will face upward if the die is rotated toward the back.

Find the minimum number of operation Snuke needs to perform in order to score at least $x$ points in total.

Constraints

• $1 ≦ x ≦ 10^{15}$
• $x$ is an integer.

Input

The input is given from Standard Input in the following format:

$x$

Output

Print the answer.

Sample Input 1

7

Sample Output 1

2

Sample Input 2

149696127901

Sample Output 2

27217477801