Description

There are $1337$ people standing in a circle. Starting from person $1$, they count numbers; the initial direction is $1,2,3\dots$. If the number someone says is a multiple of $7$ or contains the digit $7$, then the counting direction flips. Which numbered person says number $X$?

For example, for the first $20$ numbers:

Input Format

One line containing an integer $X$.

Output Format

One line containing an integer, the index of the person who says number $X$.

1000

1311

Hint

Constraints

For $30\%$ of the testdata, $X\leq10^6$.

For $90\%$ of the testdata, $X\leq10^8$.

For $100\%$ of the testdata, $X\leq10^9$.

Translated by ChatGPT 5