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C - Repsept

Score : $300$ points

Problem Statement

Takahashi loves the number $7$ and multiples of $K$.

Where is the first occurrence of a multiple of $K$ in the sequence $7,77,777,\ldots$? (Also see Output and Sample Input/Output below.)

If the sequence contains no multiples of $K$, print -1 instead.

Constraints

• $1 \leq K \leq 10^6$
• $K$ is an integer.

Input

Input is given from Standard Input in the following format:

$K$

Output

Print an integer representing the position of the first occurrence of a multiple of $K$. (For example, if the first occurrence is the fourth element of the sequence, print 4.)

101

4

None of $7$, $77$, and $777$ is a multiple of $101$, but $7777$ is.

2

-1

All elements in the sequence are odd numbers; there are no multiples of $2$.

999983

999982