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())
n = "7"*(len(str(K))+1)
m = "7"*len(str(K))
p = int(n)
ans = 0
flag = 0
if(K%2==0):
  print("-1")
elif(K==1 or K==7):
  print(1)
elif(K==77 or K==777 or K==7777 or K==77777 or K==777777):
  print(len(str(K)))
else: 
  while(ans <= K):
    ans += 1
    q = p % K
    p = str(q) + "7"
    p = int(p)
    if(q==0):
      print(ans+len(str(K)))
      flag = 1
      break
  if(flag==0):
    print("-1")