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())

def f1(i):
    count = 1
    value_n = len(str(i))
    # print(i%10)
    while i > 0:
        if i%10 == 7:
          # print(i%10)
          # print(i)
          i //= 10 # 必須
          if count == value_n:
            print(count)
            exit()
          count += 1
        else:
          i = -1
# print(len(str(K)))
if K < 7 or K % 2 ==0:
  print(-1)
  exit()

answer_flug = True
value = 0
n = 1
answer = 0
while answer_flug:
  # if len(str(K)) >= (n+1):
  if (K * n) % 7 == 0:
    f1(K * n)
  n += 1