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: Time Limit Exceeded)

# -*- coding: utf-8 -*-

def main():
    K = int(input())

    x = 7
    first = True
    flag = False
    while True:
        if(first):
            x = 7
            first = False
        else:
            x = x * 10 + 7
        
        if(x % K == 0):
            print(len(str(x)))
            flag = True
            break
    
    if(flag != True):
        print(-1)


if __name__ == "__main__":
    main()