Problem:
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.)

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

Solution in PyPy3 (7.3.0) (judge verdict: Time Limit Exceeded)

#from math import *
from collections import *
from random import *
from bisect import *
import sys
input=sys.stdin.readline
def lis():
    return list(map(int,input().split()))
def ma():
    return map(int,input().split())
def inp():
    return int(input())
n=inp()
if(n%2==0):
    print(-1)
    exit(0)
co=1
while(1):
    r=int('7'*co)
    if(co>n):
        co=-1
        break
    if(r%n==0):
        break
    co+=1
print(co)