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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)

import java.util.Scanner;

public class Main {


      public static void main(String[] args) {

            Scanner sc = new Scanner(System.in);
            int n = sc.nextInt();
            if(n%2 == 0 ){
                  System.out.println(-1);
                  System.exit(0);

            }
            int ans = 1;
            int modulo = 7;
            while(modulo%n != 0){
                  modulo = (modulo *10 + 7)%n;
                  ans++;
                  if(ans >=n){
                        ans  = -1;
                        break;

                  }            }
            System.out.println(ans);

      }


}