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.

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.)

Constraints

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

Sample Input 1

101

Sample Output 1

4

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

Sample Input 2

2

Sample Output 2

-1

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

Sample Input 3

999983

Sample Output 3

999982

见题面 Input 部分

见题面 Output 部分