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: Runtime Error)

import math

def Repsept():
    
    num = int(input())

    seven_yes = num % 7
    eleven_yes = num % 11
    mod_value = 1

    count = 1
    
    if num % 2 != 0 and num % 5 != 0:
    
        if not is_prime(num):
        
            while mod_value != 0:
                value = 7*(pow(10, count)-1)/9
                
                mod_value = value % num
    
                if mod_value != 0:
                    count = count + 1
    
            print(count)
                
        else:
            
            print(num-1)

    else:
    
        print(-1)


def is_prime(n):
    if n == 1: 
        return False

    for k in range(2, int(math.sqrt(n)) + 1):
        if n % k == 0:
            return False

    return True


if __name__ == '__main__':
    Repsept()