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)

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

    K_1 = str(K)[len(str(K)) - 1]

    if K % 2 == 0 or K_1 == "4" or K_1 == "5" or K_1 == "6" or K_1 == "8":
        print("-1")
    else:
        start_num = 0
        if K_1 == "1" :
            start_num = 7
        elif K_1 == "3":
            start_num = 9
        elif  K_1 == "7":
            start_num = 1
        elif K_1 == "9":
            start_num = 3

        while True:
            if len(str(K * start_num)) == str(K * start_num).count("7"):
                print(str(K * start_num).count("7"))
                break
            start_num = start_num + 10
main()