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 PyPy3 (7.3.0) (judge verdict: Time Limit Exceeded)

#!usr/bin/env python3
from collections import defaultdict, deque, Counter, OrderedDict
from bisect import bisect_left, bisect_right
from functools import reduce, lru_cache
from heapq import heappush, heappop, heapify

import itertools
import bisect
import math
import fractions
import sys
import copy


def L(): return sys.stdin.readline().split()


def I(): return int(sys.stdin.readline().rstrip())


def S(): return list(sys.stdin.readline().rstrip())


def LI(): return [int(x) for x in sys.stdin.readline().split()]


def LI1(): return [int(x) - 1 for x in sys.stdin.readline().split()]


def LS(): return [list(x) for x in sys.stdin.readline().split()]


def IR(n): return [I() for _ in range(n)]


def LIR(n): return [LI() for _ in range(n)]


def LIR1(n): return [LI1() for _ in range(n)]


def SR(n): return [S() for _ in range(n)]


def LSR(n): return [LS() for _ in range(n)]


def LR(n): return [L() for _ in range(n)]


alphabets = "abcdefghijklmnopqrstuvwxyz"
ALPHABETS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

sys.setrecursionlimit(1000000)
dire = [[1, 0], [0, 1], [-1, 0], [0, -1]]
dire8 = [[1, 0], [1, 1], [0, 1], [-1, 1], [-1, 0], [-1, -1], [0, -1], [1, -1]]
MOD = 1000000007


def main():
    K = I()
    ans = 1
    tmp = 7

    if K % 2 == 0:
        print(-1)
        return

    while tmp % K != 0:
        tmp *= 10
        tmp += 7
        tmp %= K
        ans += 1

    print(ans)


if __name__ == '__main__':
    main()