C - X: Yet Another Die Game

Time Limit: 2 sec / Memory Limit: 256 MB

### 問題文

すぬけくんは 6 面サイコロで遊ぶことにしました。 サイコロは 1 から 6 までの整数がそれぞれの面に書かれており、向かい合う面に書かれた数の和はどれも 7 です。

すぬけくんはサイコロの好きな面が上向きになるように置いたのち何回か以下の操作を行います。

• 操作：サイコロを手前、奥、左、右のどれかの方向に 90° だけ回転させる。その後、上を向いている面に書かれた数を y として y 点得る。

すぬけくんが合計で x 点以上得るために必要な最小の操作回数を求めなさい。

### 制約

• 1 ≦ x ≦ 10^{15}
• x は整数

### 入力

x


### 入力例 1

7


### 出力例 1

2


### 入力例 2

149696127901


### 出力例 2

27217477801


Score : 300 points

### 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


### Sample Input 1

7


### Sample Output 1

2


### Sample Input 2

149696127901


### Sample Output 2

27217477801