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 Scala (2.13.1) (judge verdict: Accepted)

import java.util.Scanner

import scala.util.control.Breaks

object Main {
  def main(args: Array[String]): Unit = {
    val sc = new Scanner(System.in)

    val k = sc.nextInt()
    var x = 7%k

    val b = new Breaks
    b.breakable {
      for(i <- 1 to k){
        if(x == 0){
          println(i)
          b.break()
        }
        x = (x*10+7)%k
      }
      println(-1)
    }

  }
}