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 Python (3.8.2) (judge verdict: Wrong Answer)

k = int(input())
if k % 2 == 0:
    print(-1)
else:
  amari = [7]
  tmp = 7
  for i in range(k+1):
      tmp = (tmp * 10) % k
      if tmp != 7:
          amari.append(tmp%k)
      else:
          break
  amari = amari * ((k//len(amari)) +1)

  ans = amari[0]
  for i in range(1, k+1):
      ans += amari[i]
      if ans % k == 0:
          print(i+1)
          break
  else:
    print(-1)