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)

k=int(input())

# mod k で考える
mod=k

for i in range(1,10**6+1):
    if mod>7*int(str(1)*i):
        continue
    else:
        if mod==k:
            mod = 7 * int(str(1) * i) % mod
            if mod == 0:
                print(i)
                exit()
        else:
            mod= (mod*10+7)%k
            if mod==0:
                print(i)
                exit()

print(-1)