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())

first_mod = 7 % K
"""
cnt = 1
if first_mod == 0:
    print(1)
else:
    flg = True
    for i in range(2,K):
        seven = old * 10 + 7
        mod = seven % K
        cnt += 1
        old = seven
        if mod == 0:
            break
        if mod == first_mod:
            flg = False
            break
    if flg:
        print(cnt)
    else:
        print(-1)
"""
old_mod = now_mod = first_mod

cnt = 1
if first_mod == 0:
    print(1)
else:
    flg = False
    for i in range(2,K):
        now_mod = ((old_mod * 10) + 7) % K
        cnt += 1
        old_mod = now_mod
        if now_mod == 0:
            flg = True
            break
        if now_mod == first_mod:
            break
    if flg:
        print(cnt)
    else:
        print(-1)