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: Accepted)

def resolve():
    '''
    code here
    '''
    K = int(input())

    is_not_found = True
    memo = [0 for _ in range(K)]

    i=7%K
    res = 1
    if i == 0:
        is_not_found = False

    while is_not_found and memo[i] == 0:
        memo[i] += 1
        if i == 0:
            is_not_found = False
        else:
            res += 1
            i = (i * 10 + 7) % K

    print(res) if is_not_found == False else print(-1)


if __name__ == "__main__":
    resolve()