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: Accepted)

K = input()
K_1 = int(K[-1])
K = int(K) 

mod_ini = 7%K
mod = 0
cnt = 0

while True:
    if K%2 == 0 or K_1 == 5:
        print(-1)
        break
    
    cnt += 1
    mod = (mod*10 + 7)%K
    #print(mod)
    
    if mod == 0:
        print(cnt)
        break
    elif mod == mod_ini and cnt != 1:
        print(-1)
        break